A rare autosomal recessive disorder causing inability to synthesize apolipoprotein B, resulting in fat malabsorption, fat-soluble vitamin deficiency, and neurological complications. Presents with acanthocytosis and severe deficiency of fat-soluble vitamins.

A chronic inflammatory skin condition of the pilosebaceous unit characterized by comedones, papules, pustules, nodules, and cysts. Affects 85% of adolescents but can persist into adulthood. Severe forms include nodulocystic acne and acne conglobata with risk of permanent scarring.

A hormonal disorder caused by excessive growth hormone production from a pituitary adenoma, usually after puberty. Causes gradual enlargement of bones and tissues, particularly hands, feet, and face.

The most common childhood cancer, characterized by uncontrolled proliferation of immature lymphoid cells (lymphoblasts) in bone marrow and blood. Peak incidence at 2-5 years. Multiple subtypes with varying prognosis.

A neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. Begins in childhood and often persists into adulthood. Affects approximately 5-7% of children and 2.5-4% of adults globally. Three subtypes: predominantly inattentive, predominantly hyperactive-impulsive, and combined.

Progressive degenerative disease of the macula causing central vision loss. Leading cause of irreversible blindness in adults over 50 in developed countries. Dry (atrophic) and wet (neovascular) forms.

A genetic disorder affecting the collagen network of the glomerular basement membrane, causing progressive kidney disease, hearing loss, and eye abnormalities. Caused by mutations in COL4A3, COL4A4, or COL4A5 genes. X-linked form most common and severe in males.

A neurogenetic disorder caused by deletion or mutation of UBE3A gene on maternal chromosome 15. Characterized by severe developmental delay, speech impairment, ataxia, seizures, and happy demeanor with frequent laughing/smiling.

A chronic inflammatory arthritis primarily affecting the axial skeleton (spine and sacroiliac joints), causing pain, stiffness, and potential fusion. A form of spondyloarthritis. Strong association with HLA-B27. Onset typically in young adulthood.

A group of mental health conditions characterized by excessive fear, worry, and related behavioral disturbances. Generalized Anxiety Disorder (GAD) involves persistent, uncontrollable worry about everyday things. Most common mental health disorder.

Chronic inflammatory airway disease causing reversible bronchospasm, wheezing, dyspnea. Affects 262 million globally. Can be life-threatening during severe attacks.

The most common sustained cardiac arrhythmia, characterized by chaotic electrical activity in the atria leading to irregular ventricular response. Increases risk of stroke five-fold and heart failure. Prevalence increases with age, affecting ~10% of people over 80.

A complex neurodevelopmental condition characterized by challenges with social communication and interaction, and restricted, repetitive patterns of behavior, interests, or activities. Spectrum disorder ranging from mild to severe. Affects approximately 1-2% of population, more common in males.

A chronic liver disease in which the immune system attacks the liver, causing inflammation and potentially leading to cirrhosis and liver failure. Can occur at any age, more common in women. Often associated with other autoimmune conditions.

A group of disorders characterized by autoimmune destruction of multiple endocrine glands. Type 1 (AIRE gene): mucocutaneous candidiasis, hypoparathyroidism, adrenal insufficiency. Type 2: adrenal insufficiency, autoimmune thyroid disease, type 1 diabetes.

A group of renal tubular disorders affecting salt reabsorption in thick ascending limb of Henle. Characterized by salt wasting, hypokalemia, metabolic alkalosis, and hypercalciuria. Several genetic types with different severity.

A mental health condition causing extreme mood swings including emotional highs (mania/hypomania) and lows (depression). Formerly called manic depression. Types I and II. Affects approximately 2.8% of adults globally.

Hereditary cancer syndrome caused by mutations in BRCA1 or BRCA2 tumor suppressor genes. Significantly increased lifetime risk of breast cancer (up to 70%), ovarian cancer (up to 44%), prostate cancer, and pancreatic cancer.

A chronic lung condition characterized by permanent abnormal dilation and destruction of bronchial walls, leading to impaired mucus clearance, recurrent infections, and progressive lung damage. Often underdiagnosed. Can be post-infectious or associated with underlying conditions.

A clouding of the normally clear lens of the eye, leading to decreased vision. Most commonly age-related but can be congenital or secondary to other conditions. Leading cause of blindness globally but highly treatable.

A group of progressive neurodegenerative disorders (Batten disease) causing accumulation of lipopigments in neurons. Multiple types with different ages of onset. Cause blindness, seizures, dementia, and premature death.

The most common inherited neurological disorder (hereditary motor and sensory neuropathy), affecting peripheral nerves. Progressive muscle weakness and sensory loss, particularly in feet and hands. Multiple genetic subtypes.

A group of inherited immunodeficiencies affecting phagocytic cells' ability to kill intracellular pathogens due to NADPH oxidase defects. X-linked (CYBB) most common; autosomal recessive forms (CYBA, NCF1, NCF2, NCF4) also occur.

Progressive, irreversible loss of kidney function over months to years. Stage 4 (eGFR 15-29 mL/min) and Stage 5/end-stage renal disease (eGFR <15 mL/min or dialysis). Requires renal replacement therapy. Leading causes: diabetes and hypertension.

A progressive inflammatory disease of the pancreas causing permanent structural damage and loss of function. Characterized by chronic abdominal pain, exocrine insufficiency (malabsorption), and endocrine insufficiency (diabetes). Most commonly caused by alcohol.

End-stage liver disease characterized by replacement of normal hepatic architecture with fibrosis and regenerative nodules. Results from chronic liver injury. Irreversible but progression can be halted.

Congenital facial malformations occurring when tissues don't fuse properly during fetal development. Can affect lip alone, palate alone, or both. Most common craniofacial birth defect. Multifactorial etiology with genetic and environmental components.

An extremely painful primary headache disorder characterized by severe unilateral orbital, supraorbital, or temporal pain lasting 15-180 minutes, occurring in clusters (periods of frequent attacks). Known as 'suicide headache' due to intensity. More common in men.

The most common symptomatic primary immunodeficiency in adults, characterized by hypogammaglobulinemia with impaired antibody responses. Diverse genetic causes in subset; often sporadic. Increased risk of autoimmune disease and lymphoma.

A group of autosomal recessive disorders affecting adrenal steroidogenesis. Most common is 21-hydroxylase deficiency causing cortisol and aldosterone deficiency with androgen excess. Can cause life-threatening salt-wasting crisis in newborns.

Opacification of the lens present at birth or developing in early childhood. Can be isolated or associated with genetic syndromes, metabolic disorders, or intrauterine infections. Leading treatable cause of childhood blindness.

A birth defect where the diaphragm fails to form completely, allowing abdominal organs to move into the chest and compress lungs. Causes pulmonary hypoplasia and pulmonary hypertension. Life-threatening condition requiring immediate intervention.

A group of structural heart defects present at birth that require intervention in infancy. Includes hypoplastic left heart syndrome, transposition of the great arteries, tetralogy of Fallot, coarctation of aorta, and single ventricle defects.

A group of muscular dystrophies presenting at birth or early infancy with hypotonia, muscle weakness, and contractures. Multiple subtypes including merosin-deficient, Ullrich, and LMNA-related. Variable severity and progression.

Advanced chronic obstructive pulmonary disease (GOLD grades 3-4, FEV1 <50% predicted). Characterized by persistent respiratory symptoms and airflow limitation. Third leading cause of death globally. Severe disease significantly impairs quality of life and increases mortality.

Respiratory illness caused by SARS-CoV-2 virus. Global pandemic 2020-2023. Range from asymptomatic to severe pneumonia, ARDS, death. Long COVID affects millions.

Persistent symptoms following acute COVID-19 infection, lasting weeks to months after initial recovery. Affects multiple organ systems. Estimated 10-30% of COVID-19 survivors develop long COVID. Symptoms can be debilitating and fluctuating.

Premature fusion of one or more cranial sutures leading to abnormal skull shape. Can be isolated or part of syndromes (Apert, Crouzon, Pfeiffer). Increased intracranial pressure risk with multiple suture involvement.

An inherited disorder of renal amino acid transport causing excessive urinary excretion of cystine and other dibasic amino acids. Cystine precipitates forming recurrent kidney stones (cystine calculi), potentially leading to renal damage.

Cognitive decline caused by impaired blood flow to the brain, typically from strokes or small vessel disease. Second most common dementia after Alzheimer's. Often coexists with Alzheimer's (mixed dementia). Stepwise progression correlating with vascular events.

An X-linked recessive renal tubular disorder caused by CLCN5 or OCRL1 mutations. Characterized by low-molecular-weight proteinuria, hypercalciuria, nephrocalcinosis, kidney stones, and progressive renal failure. Often presents in childhood.

A disorder of water balance causing excessive urination and thirst due to insufficient ADH (central DI) or kidney resistance to ADH (nephrogenic DI). Distinct from diabetes mellitus despite similar name.

An autoimmune condition where the pancreas produces little or no insulin. Previously known as juvenile diabetes, it typically appears during childhood or adolescence but can develop in adults. Requires lifelong insulin therapy.

A chronic metabolic disorder characterized by high blood sugar, insulin resistance, and relative lack of insulin. The most common form of diabetes, accounting for 90-95% of cases. Often preventable and sometimes reversible with lifestyle changes.

A diabetes complication affecting the eyes, caused by damage to blood vessels in the retina. Leading cause of blindness in working-age adults. Can progress from mild non-proliferative to proliferative retinopathy with neovascularization.

A condition in which the heart's main pumping chamber (left ventricle) becomes enlarged and weakened, reducing the heart's ability to pump blood effectively. Can lead to heart failure and sudden cardiac death.

A rare but severe, often fatal hemorrhagic fever caused by Ebola virus. Zoonotic disease transmitted from wild animals to humans, then human-to-human. Case fatality rate 25-90% depending on outbreak. West Africa 2014-2016 outbreak: 28,000+ cases.

A chronic, relapsing inflammatory skin condition characterized by intense itching, dry skin, and eczematous lesions. Part of the 'atopic triad' with asthma and allergic rhinitis. Affects up to 20% of children and 10% of adults. Often begins in infancy.

A muscular dystrophy characterized by joint contractures (elbows, ankles, spine), slowly progressive muscle wasting and weakness, and cardiac conduction defects. X-linked (EDMD1/EMD), autosomal dominant (EDMD2/LMNA, EDMD3), and recessive forms.

Chronic neurological disorder characterized by recurrent, unprovoked seizures due to excessive neuronal activity in brain. Affects 50 million people worldwide. Many types: focal, generalized, unknown onset. Often begins in childhood or after age 65.

The second most common bone tumor in children and adolescents, characterized by EWSR1-ETS gene fusions. Can occur in bone or soft tissue (extraosseous Ewing). Peak incidence in adolescence. Highly aggressive but chemotherapy-responsive.

The third most common muscular dystrophy, characterized by progressive weakness of facial, scapular, and humeral muscles. Caused by abnormal expression of DUX4 gene due to contraction of D4Z4 repeats. Variable severity even within families.

An inherited disorder of cholesterol metabolism causing severely elevated LDL cholesterol from birth. Autosomal dominant. Heterozygous: 1 in 250; Homozygous: 1 in 300,000. Causes premature cardiovascular disease if untreated.

A rare inherited bone marrow failure syndrome caused by mutations in DNA repair genes. Characterized by pancytopenia, congenital abnormalities, and increased risk of leukemia and solid tumors. 22 different complementation groups identified.

A condition in which excess fat builds up in the liver, not due to alcohol use. The most common chronic liver disease worldwide, affecting 25% of the global population. Ranges from simple steatosis to nonalcoholic steatohepatitis (NASH) which can progress to cirrhosis.

A chronic disorder characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and cognitive difficulties. Central sensitization syndrome where pain signals are amplified. Affects 2-4% of population, predominantly women.

A rare disorder of HDL metabolism caused by LCAT deficiency. Named for corneal opacities that resemble fish eyes. Very low HDL cholesterol but milder than complete LCAT deficiency. Cardiovascular risk unclear.

A rare kidney disorder characterized by scarring (sclerosis) in scattered regions (focal) of the kidney's glomeruli (segmental). It is a leading cause of nephrotic syndrome and end-stage renal disease. Can be primary (idiopathic) or secondary to various conditions including genetic mutations, infections, or drug toxicity.

The most common inherited ataxia, caused by GAA triplet repeat expansion in FXN gene. Progressive gait ataxia, sensory neuropathy, cardiomyopathy, and diabetes. Autosomal recessive. Onset typically adolescence.

An inherited disorder affecting galactose metabolism due to deficiency of GALT, GALK, or GALE enzymes. Classic galactosemia (GALT deficiency) is most severe. Galactose-1-phosphate accumulates, causing multi-organ damage if untreated.

Inflammation of the stomach lining. Can be acute (sudden onset) or chronic (long-term). Common causes include H. pylori infection, NSAID use, and excessive alcohol consumption. Can lead to ulcers and increased stomach cancer risk if untreated.

A chronic digestive disease where stomach acid or bile irritates the food pipe lining. Occurs when the lower esophageal sphincter relaxes abnormally or weakens. Affects approximately 20% of adults in Western countries. Can lead to serious complications if untreated.

A congenital abdominal wall defect where intestines protrude through a defect usually to the right of the umbilicus. Not covered by protective membrane (unlike omphalocele). Increasing incidence worldwide, especially in young mothers.

Diabetes diagnosed for the first time during pregnancy. Affects approximately 2-10% of pregnancies worldwide. Increases risk of complications for both mother and baby but usually resolves after delivery. Women with GDM have 50% lifetime risk of developing type 2 diabetes.

An intestinal infection caused by the parasite Giardia lamblia (also called Giardia intestinalis or duodenalis). Common waterborne disease causing diarrhea, gas, and stomach cramps. Most common intestinal parasitic disease in US.

A benign genetic condition causing mild unconjugated hyperbilirubinemia due to reduced UDP-glucuronosyltransferase activity. Affected individuals have intermittent mild jaundice, often triggered by fasting, illness, or stress. No treatment needed.

A renal tubular disorder caused by SLC12A3 mutations affecting thiazide-sensitive NaCl cotransporter. Characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. Milder than Bartter syndrome, often diagnosed in adolescence/adulthood.

A group of eye conditions damaging the optic nerve, often due to abnormally high pressure in the eye (intraocular pressure). Leading cause of irreversible blindness worldwide. Primary open-angle glaucoma most common; angle-closure glaucoma is emergency.

A rare autoimmune disease where antibodies attack the basement membrane in lungs and kidneys, causing rapidly progressive glomerulonephritis and pulmonary hemorrhage. Medical emergency with high mortality if untreated.

A chronic inflammatory arthritis caused by hyperuricemia and deposition of monosodium urate crystals in joints and tissues. Characterized by recurrent acute flares and progressive joint damage. Associated with metabolic syndrome, cardiovascular disease, and chronic kidney disease.

An acute inflammatory demyelinating polyradiculoneuropathy causing rapid-onset muscle weakness and paralysis. Autoimmune attack on peripheral nerves, often triggered by infections. Medical emergency requiring immediate treatment.

The most common cause of hypothyroidism in iodine-sufficient regions. An autoimmune disorder where antibodies (anti-TPO, anti-thyroglobulin) attack the thyroid gland. Strongly associated with other autoimmune diseases. More common in women (5-10:1).

Structural abnormalities of one or more heart valves (aortic, mitral, tricuspid, pulmonic) causing stenosis (narrowing) or regurgitation (leakage). Can be congenital or acquired. Aortic stenosis most common in elderly; rheumatic heart disease prevalent in developing countries.

Rare inherited bleeding disorders caused by deficiency in clotting factor VIII (Hemophilia A) or IX (Hemophilia B/Christmas disease). X-linked recessive inheritance affecting primarily males. Characterized by prolonged bleeding after injury, surgery, or spontaneous bleeding into joints and muscles.

Viral infection causing liver inflammation, transmitted via blood. Often chronic, leading to cirrhosis and liver cancer. Curable with direct-acting antivirals (DAAs). 58 million chronically infected.

A viral infection caused by hepatitis C virus (HCV) that causes liver inflammation, potentially leading to cirrhosis, hepatocellular carcinoma, and liver failure. Chronic infection develops in 75-85% of acute cases. Curable with direct-acting antivirals.

The most common malignant liver tumor in children, usually occurring before age 3. Associated with prematurity, low birth weight, and Beckwith-Wiedemann syndrome. Rising incidence correlates with improved survival of premature infants.

An autosomal dominant disorder causing recurrent episodes of severe swelling (angioedema) affecting skin, gastrointestinal tract, and airway. Caused by C1 inhibitor deficiency (HAE types I/II) or factor XII mutation (HAE type III).

Protrusion of an organ or tissue through an abnormal opening, commonly occurring in the abdominal wall. Inguinal hernias most common in men, umbilical and incisional hernias also frequent. Can lead to serious complications if strangulated.

A lifelong viral infection with two types: HSV-1 (primarily oral, increasingly genital) and HSV-2 (primarily genital). Virus establishes latency in sensory ganglia. Reactivates periodically causing recurrent outbreaks. Highly prevalent worldwide.

Human Immunodeficiency Virus attacks CD4+ T cells, progressively weakening the immune system. Without treatment, progresses to Acquired Immunodeficiency Syndrome (AIDS). Transmitted through blood, sexual contact, and mother-to-child. First described in 1981.

A lymphoid malignancy characterized by Reed-Sternberg cells in lymph nodes. Bimodal age distribution (young adults and elderly). Two main types: classical Hodgkin lymphoma (nodular sclerosis, mixed cellularity, lymphocyte-rich, lymphocyte-depleted) and nodular lymphocyte-predominant.

The most common sexually transmitted infection. Over 200 types exist; low-risk types cause warts, high-risk types (16, 18, 31, 33, 45, etc.) cause cancers. Virus persists in epithelial cells. Most infections clear spontaneously but some become persistent.

Overproduction of parathyroid hormone (PTH) usually due to a parathyroid adenoma, causing hypercalcemia. Most common cause of hypercalcemia in outpatients. Often asymptomatic but can cause kidney stones, osteoporosis, and neuropsychiatric symptoms.

A condition where the thyroid gland produces too much thyroid hormone (T3 and T4). Accelerates the body's metabolism, causing unintentional weight loss, rapid heartbeat, sweating, and nervousness. Graves' disease is the most common cause.

A genetic condition characterized by abnormal thickening (hypertrophy) of the heart muscle, most commonly the interventricular septum. Can obstruct blood flow and cause arrhythmias. Leading cause of sudden cardiac death in young athletes.

Deficiency of parathyroid hormone causing hypocalcemia and hyperphosphatemia. Most commonly due to thyroid/parathyroid surgery; can be autoimmune, genetic (DiGeorge, activating CaSR mutations), or idiopathic.

Deficiency of one or more pituitary hormones affecting growth, metabolism, reproduction, and stress response. Can be congenital, due to tumors, trauma, radiation, or autoimmune. Requires lifelong hormone replacement.

A condition where the thyroid gland doesn't produce enough thyroid hormones. Slows down many of the body's functions. Hashimoto's thyroiditis is the most common cause in developed countries. Can occur at any age but is more common in older women.

A chronic, progressive, and ultimately fatal lung disease characterized by scarring (fibrosis) of the lung tissue without known cause. The fibrosis is irreversible and leads to progressive decline in lung function, making breathing increasingly difficult.

Viral respiratory infection caused by influenza A and B viruses. Annual epidemics causing significant morbidity and mortality. Vaccine composition updated yearly.

A large group of disorders characterized by inflammation and scarring of the interstitium (tissue and space around air sacs). Includes over 200 different conditions, many of unknown cause. Progressive fibrosis leads to impaired gas exchange and respiratory failure.

A common functional gastrointestinal disorder affecting the large intestine, characterized by abdominal pain and altered bowel habits (diarrhea, constipation, or both). Brain-gut interaction disorder without structural abnormalities. Affects 10-15% of global population.

A progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape, causing distorted vision. Typically affects both eyes and begins during puberty or late teens.

Recurrent formation of solid mineral deposits in the kidneys, causing severe pain and potential kidney damage. Affects 1 in 10 people; 50% recurrence rate within 5-10 years without preventive measures. Most common type: calcium oxalate.

A mitochondrial disorder causing sudden, painless vision loss in young adults, typically males. Caused by mutations in mitochondrial DNA (MT-ND1, MT-ND4, MT-ND6, MT-ND4L). Usually affects one eye first, then the other within weeks to months.

A severe neurological disorder characterized by progressive loss of mental and movement abilities, typically beginning in infancy or childhood. Caused by mitochondrial dysfunction affecting brainstem and basal ganglia. Many genetic causes.

A myeloproliferative neoplasm characterized by the Philadelphia chromosome (t(9;22)) creating the BCR-ABL fusion gene, leading to constitutively active tyrosine kinase. Chronic phase is indolent; without treatment progresses to accelerated phase and blast crisis.

An autosomal dominant disorder causing severe early-onset hypertension and hypokalemia due to constitutive activation of epithelial sodium channel (ENaC). Mimics hyperaldosteronism but aldosterone is suppressed. Responds to amiloride/triamterene.

A group of inherited muscular dystrophies affecting shoulder and pelvic girdle muscles. Multiple genetic subtypes with autosomal dominant (LGMD1) and recessive (LGMD2) inheritance. Variable age of onset and progression.

The progressive form of non-alcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis with inflammation and hepatocyte injury, with or without fibrosis. Can progress to cirrhosis and hepatocellular carcinoma. Now called MASH (metabolic dysfunction-associated steatohepatitis).

A heart rhythm disorder that can potentially cause fast, chaotic heartbeats (torsades de pointes), leading to fainting, seizures, or sudden death. The QT interval on ECG is prolonged, indicating delayed ventricular repolarization.

Malignant tumor arising from lung tissue. Leading cause of cancer death worldwide (1.8 million deaths/year). Two main types: non-small cell (NSCLC, 85%) and small cell (SCLC, 15%). Strongly associated with smoking but affects non-smokers too.

Kidney inflammation caused by systemic lupus erythematosus (SLE), affecting 40-60% of lupus patients. Can lead to proteinuria, hematuria, hypertension, and end-stage kidney disease. Six histological classes with varying prognosis.

A common but serious mood disorder causing persistent feelings of sadness and loss of interest. Affects approximately 280 million people worldwide, leading cause of disability globally. Can occur at any age.

A group of monogenic diabetes disorders characterized by early onset (usually <25 years), autosomal dominant inheritance, and beta-cell dysfunction. Multiple genetic subtypes with different clinical features and treatment responses.

The most common malignant brain tumor in children, arising in the cerebellum (posterior fossa). Embryonal tumor with multiple molecular subgroups (WNT, SHH, Group 3, Group 4) with different prognoses. Can spread through CSF.

A malignant tumor of melanocytes, the pigment-producing cells of the skin. The most serious form of skin cancer with high metastatic potential. Incidence rising globally, particularly in fair-skinned populations. Early detection critical for survival.

Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes. A maternally inherited mitochondrial disorder characterized by stroke-like episodes before age 40, seizures, dementia, and myopathy. Most commonly caused by m.3243A>G mutation.

A disorder of the inner ear causing episodes of vertigo, fluctuating hearing loss, tinnitus, and aural fullness. Caused by abnormal fluid buildup in the inner ear (endolymphatic hydrops). Affects approximately 12-30 per 100,000 people.

A life-threatening infection of the meninges (membranes surrounding the brain and spinal cord) caused by bacteria. Medical emergency requiring immediate antibiotic treatment. Can cause brain damage, hearing loss, and death. Vaccines available for some types.

A rare X-linked disorder of copper metabolism caused by ATP7A mutations. Copper deficiency leads to progressive neurodegeneration, connective tissue abnormalities, and distinctive kinky hair. Fatal in early childhood without treatment.

Advanced skin cancer that has spread to lymph nodes or distant organs (stage III/IV). While treatments have dramatically improved survival, metastatic melanoma remains incurable for most patients. Often involves BRAF V600 mutations (~50%).

A primary headache disorder characterized by recurrent attacks of moderate to severe throbbing pain, usually on one side of the head, often accompanied by nausea, vomiting, and sensitivity to light and sound. Can last 4-72 hours. Second most disabling condition worldwide.

A kidney disorder that causes nephrotic syndrome, most commonly in children. Characterized by normal-appearing glomeruli on light microscopy with podocyte foot process effacement visible only on electron microscopy. Also called nil disease or lipoid nephrosis.

A group of disorders caused by dysfunction of mitochondria, the cell's energy-producing organelles. Can affect any organ system. Extremely heterogeneous presentation. Can be caused by mitochondrial DNA or nuclear DNA mutations.

A contagious disease most commonly caused by Epstein-Barr virus (EBV). Characterized by fever, sore throat, swollen lymph nodes, and fatigue. Often called 'mono' or 'kissing disease' due to transmission via saliva. Most common in adolescents and young adults.

A group of inherited syndromes causing tumors in multiple endocrine glands. MEN1 (menin gene): parathyroid, pituitary, pancreas. MEN2 (RET gene): medullary thyroid carcinoma, pheochromocytoma, parathyroid hyperplasia.

A malignancy of plasma cells characterized by clonal proliferation in bone marrow, monoclonal protein production, and end-organ damage (CRAB: hyperCalcemia, Renal insufficiency, Anemia, Bone lesions). Median age at diagnosis 69 years.

The most common adult muscular dystrophy, caused by CTG repeat expansion in DMPK (DM1) or CCTG in CNBP (DM2). Multisystem disorder with myotonia, progressive muscle weakness, cardiac conduction abnormalities, cataracts, and endocrine dysfunction.

A clinical syndrome characterized by massive proteinuria (>3.5g/day), hypoalbuminemia, edema, and hyperlipidemia. Not a single disease but a manifestation of various glomerular disorders including minimal change disease, FSGS, membranous nephropathy, and diabetic nephropathy.

Congenital defects of the brain, spine, or spinal cord due to failure of neural tube closure in early pregnancy. Includes anencephaly, encephalocele, and spina bifida (myelomeningocele, meningocele). Folic acid deficiency major risk factor.

The most common extracranial solid tumor in childhood, arising from neural crest cells of the adrenal medulla or sympathetic nervous system. Highly variable clinical behavior ranging from spontaneous regression to aggressive metastatic disease.

Complex chronic disease characterized by excessive adipose tissue accumulation (BMI >=35). Associated with metabolic dysfunction, inflammation, and increased morbidity/mortality. Now recognized as relapsing-remitting disease requiring long-term management.

A chronic mental health disorder characterized by uncontrollable, recurring thoughts (obsessions) and behaviors (compulsions) that the person feels compelled to repeat. Often time-consuming and interferes with daily life.

A late-onset muscular dystrophy characterized by ptosis (drooping eyelids) and dysphagia (difficulty swallowing). Caused by GCG repeat expansion in PABPN1 gene. Onset typically 40-60 years. More common in certain populations (French-Canadian, Bukhara Jews).

Inflammation of the optic nerve causing vision loss, usually in one eye. Often associated with multiple sclerosis but can occur in isolation or with other demyelinating diseases. Typically affects young adults.

A systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and fracture risk. Often called the 'silent disease' because bone loss occurs without symptoms until fracture occurs.

The most common primary malignant bone tumor in children and adolescents, typically occurring at metaphysis of long bones. Associated with rapid growth and TP53 mutations. Peak incidence during adolescent growth spurt.

Open sores that develop on the inside lining of the stomach (gastric ulcers) and the upper portion of the small intestine (duodenal ulcers). Most common cause is H. pylori infection or NSAID use. Affects approximately 4% of the global population.

Infection causing inflammation of lung air sacs (alveoli). Can be bacterial, viral, or fungal. Leading cause of death in children worldwide and serious illness in elderly.

A common hormonal disorder affecting women of reproductive age, characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries. Leading cause of infertility. Associated with metabolic syndrome and increased cardiovascular risk.

A group of rare genetic disorders causing overproduction of oxalate, leading to calcium oxalate kidney stones, nephrocalcinosis, and end-stage renal disease. Three types with different enzyme deficiencies (AGXT, GRHPR, HOGA1).

A chronic immune-mediated inflammatory skin disease characterized by well-demarcated, erythematous plaques with silvery scale. Affects 2-3% of global population. Associated with psoriatic arthritis, cardiovascular disease, and metabolic syndrome.

A mental health condition triggered by experiencing or witnessing a terrifying event. Characterized by intrusive memories, avoidance, negative changes in thinking and mood, and hyperarousal. Can develop after combat, assault, accidents, or natural disasters.

A rare but serious condition characterized by high blood pressure in the pulmonary arteries, leading to right heart failure. Group 1 PAH is a progressive disease affecting the small pulmonary arteries, causing vessel narrowing and increased resistance to blood flow.

A fatal viral disease affecting the central nervous system, transmitted through saliva of infected animals. Once clinical symptoms appear, rabies is virtually 100% fatal. Preventable through post-exposure prophylaxis (PEP) if administered before symptom onset.

A clinical syndrome characterized by rapid loss of kidney function over days to weeks, with crescent formation visible on kidney biopsy. Crescentic glomerulonephritis represents severe kidney inflammation requiring urgent treatment.

A group of disorders affecting the kidney tubules' ability to maintain acid-base balance, leading to metabolic acidosis. Types include distal (Type 1), proximal (Type 2), and hypoaldosteronism-related (Type 4). Can cause growth retardation in children and kidney stones.

The most common intraocular malignancy in children, caused by RB1 tumor suppressor gene mutations. Can be unilateral (usually non-hereditary) or bilateral (hereditary). Early detection critical for vision preservation and survival.

A potentially blinding eye disorder affecting premature infants, caused by abnormal blood vessel development in the retina. Risk increases with lower gestational age and birth weight. Leading cause of childhood blindness in developed countries.

The most common soft tissue sarcoma in children, arising from skeletal muscle progenitors. Two main types: embryonal (including botryoid and spindle cell variants) and alveolar. Can occur anywhere in body including head/neck, genitourinary, and extremities.

A chronic inflammatory autoimmune disease primarily affecting synovial joints, causing painful swelling and potential joint deformity and bone erosion. Systemic features can affect cardiovascular, pulmonary, and other organ systems. Affects women 2-3 times more than men.

The most common chronic rheumatic disease in children, characterized by persistent joint inflammation lasting >6 weeks in children <16 years. Multiple subtypes including oligoarticular, polyarticular, and systemic (Still's disease). Can cause permanent joint damage and growth abnormalities.

A multisystem inflammatory disease characterized by formation of non-caseating granulomas, most commonly affecting the lungs and lymph nodes. Of unknown cause, thought to involve abnormal immune response to environmental triggers in genetically susceptible individuals.

Severe chronic mental disorder characterized by disruptions in thought processes, perceptions, emotional responsiveness, and social interactions. Involves positive symptoms (hallucinations, delusions), negative symptoms (apathy, withdrawal), and cognitive impairment.

A life-threatening organ dysfunction caused by a dysregulated host response to infection. Medical emergency with high mortality. Septic shock is a subset with circulatory and cellular/metabolic dysfunction. Leading cause of death in hospitals.

A group of rare disorders causing extreme insulin resistance. Includes type A insulin resistance (INSR mutations), type B (autoantibodies), leprechaunism, and lipodystrophies. Causes severe metabolic abnormalities despite high insulin levels.

A sleep-related breathing disorder characterized by recurrent episodes of complete or partial upper airway obstruction during sleep, causing apneas or hypopneas. Leads to fragmented sleep, daytime sleepiness, and cardiovascular complications. Often undiagnosed.

An autosomal recessive motor neuron disease caused by SMN1 gene mutations affecting survival motor neuron protein. Progressive muscle weakness and atrophy. SMA type 1 (infantile) is most severe; SMA type 4 (adult-onset) is mildest.

A group of autosomal dominant neurodegenerative disorders characterized by progressive cerebellar ataxia. Multiple subtypes (SCA1, SCA2, SCA3/Machado-Joseph, etc.) caused by CAG repeat expansions or other mutations. Variable features.

A bacterial infection of the throat and tonsils caused by group A Streptococcus (GAS). Common in children but can affect all ages. If untreated, can lead to serious complications including rheumatic fever and post-streptococcal glomerulonephritis.

Acute cerebral infarction caused by interruption of blood supply to the brain, typically from thrombosis or embolism. The most common type of stroke (85% of all strokes). Time-critical emergency requiring rapid intervention. Leading cause of disability worldwide.

A rare disorder of cholesterol transport caused by ABCA1 mutations, causing extremely low HDL cholesterol and accumulation of cholesterol in tissues. Large orange-yellow tonsils are characteristic. Increased cardiovascular risk.

The most common solid tumor in young men (15-35 years). Two main types: germ cell tumors (seminoma and non-seminoma) and non-germ cell tumors. Highly curable even when metastatic. Associated with cryptorchidism and family history.

A benign genetic condition characterized by uniformly thinned glomerular basement membranes on kidney biopsy, causing persistent microscopic hematuria. Also called benign familial hematuria. Usually non-progressive with excellent long-term prognosis.

A parasitic disease caused by Toxoplasma gondii. Most people experience no symptoms, but can cause serious complications in pregnant women and immunocompromised individuals. Transmitted through undercooked meat, cat feces, and mother-to-child.

Bacterial infection caused by Mycobacterium tuberculosis, primarily affecting lungs but can involve any organ. Leading infectious cause of death worldwide. Latent infection common; active disease in 5-10% of infected.

Autoimmune destruction of pancreatic beta cells causing absolute insulin deficiency. Requires lifelong exogenous insulin. Onset typically in childhood/adolescence but can occur at any age.

Progressive metabolic disorder characterized by insulin resistance and relative insulin deficiency. Accounts for 90-95% of diabetes cases. Strongly associated with obesity and sedentary lifestyle.

Benign smooth muscle tumors of the uterus, extremely common in women of reproductive age. Can cause heavy bleeding, pain, and reproductive issues. Vary greatly in size from microscopic to massive tumors distorting the uterus.

An autoimmune disorder characterized by loss of melanocytes resulting in depigmented patches of skin and hair. Affects 0.5-2% of global population. Can be segmental (limited) or non-segmental (generalized). Associated with other autoimmune diseases.

A mosquito-borne flavivirus most commonly transmitted by Culex species mosquitoes. Can cause neurological disease in humans. Birds are primary hosts. First identified in Uganda in 1937; emerged in North America in 1999.

The most common renal malignancy in children, typically affecting ages 3-4 years. Often associated with WT1 or WT2 gene mutations. Can be part of syndromes (WAGR, Denys-Drash, Beckwith-Wiedemann). Excellent prognosis with treatment.

The first described primary immunodeficiency, caused by BTK gene mutations leading to absent B cells and severe hypogammaglobulinemia. Affected males develop recurrent bacterial infections starting after 6 months when maternal antibodies wane.

X-linked lysosomal storage disorder causing accumulation of globotriaosylceramide due to alpha-galactosidase A deficiency. Affects multiple organs including kidneys (proteinuria, progressive renal failure), heart, and nervous system. Renal involvement is major cause of morbidity.

A group of autosomal recessive disorders affecting methionine metabolism. Most common form is cystathionine beta-synthase deficiency. Characterized by lens dislocation, intellectual disability, thromboembolism, and skeletal abnormalities. Responds to pyridoxine (B6) in some patients.

A group of hereditary disorders affecting tyrosine metabolism. Type I most severe, caused by fumarylacetoacetate hydrolase deficiency. Causes liver failure, renal dysfunction, and neurologic crises. Types II and III less severe with mainly skin/eye or developmental symptoms.

A group of inherited metabolic disorders affecting the urea cycle, leading to hyperammonemia. Can present as life-threatening neonatal encephalopathy or later with episodic hyperammonemia. OTC deficiency most common in females; CPS1, ASS, ASL deficiencies also occur.

The most common fatty acid oxidation disorder, caused by ACADM gene mutations. Presents with hypoketotic hypoglycemia during fasting or illness. Can lead to seizures, coma, and sudden death if untreated. Excellent prognosis with proper management.

The most common lysosomal storage disorder, caused by glucocerebrosidase deficiency. Characterized by hepatosplenomegaly, cytopenias, and bone disease. Non-neuronopathic form (Type 1) accounts for 90% of cases. Most common in Ashkenazi Jewish population.

The severe form of MPS I caused by alpha-L-iduronidase deficiency. Characterized by multisystem involvement including coarse facies, skeletal abnormalities, intellectual disability, cardiac disease, and hepatosplenomegaly. Rapid progression without treatment.

The most common glycogen storage disease, caused by glucose-6-phosphatase deficiency (Type Ia) or translocase deficiency (Type Ib). Characterized by severe fasting hypoglycemia, hepatomegaly, lactic acidosis, hyperuricemia, and hyperlipidemia.

A genetic disorder causing low levels of alpha-1 antitrypsin, leading to panacinar emphysema, particularly in the lower lobes. Patients develop early-onset COPD, often before age 45. Can also cause liver disease.

A form of pulmonary hypertension caused by chronic obstruction of pulmonary arteries due to organized thrombi. Develops in 2-4% of patients after acute pulmonary embolism. Potentially curable with pulmonary endarterectomy.

A rare lung disease characterized by proliferation of abnormal smooth muscle-like cells (LAM cells) causing cystic destruction of lung tissue. Almost exclusively affects women. Associated with tuberous sclerosis complex or sporadic. Can cause pneumothorax and chylous effusions.

A progressive cardiomyopathy characterized by fibrofatty replacement of the myocardium, predominantly affecting the right ventricle. Major cause of sudden cardiac death in young athletes, especially in Mediterranean populations.

An inherited channelopathy characterized by specific ECG pattern (coved ST elevation) in V1-V3 and increased risk of ventricular fibrillation and sudden cardiac death. Most common in Southeast Asian males. Often presents during sleep or fever.

A congenital heart condition characterized by an accessory atrioventricular pathway (bundle of Kent) allowing pre-excitation. Associated with paroxysmal supraventricular tachycardia and risk of sudden cardiac death from atrial fibrillation with rapid ventricular response.

The least common cardiomyopathy characterized by stiff ventricles with impaired diastolic filling but preserved systolic function. Can be idiopathic, genetic, or secondary to infiltrative diseases (amyloidosis, sarcoidosis, hemochromatosis).

A rare condition caused by obstruction of hepatic venous outflow from thrombosis of hepatic veins or inferior vena cava. Acute form is life-threatening; chronic form causes cirrhosis. Associated with hypercoagulable states.

The most common genetic disorder in populations of Northern European descent, causing iron overload due to increased intestinal absorption. Leads to cirrhosis, hepatocellular carcinoma, and liver failure if untreated. HFE C282Y homozygosity most common.

Liver disease caused by accumulation of misfolded alpha-1 antitrypsin protein in hepatocytes. Can present as neonatal cholestasis, childhood cirrhosis, or adult chronic liver disease. Same genetic defect causing pulmonary disease.

A rare glycogen storage disease caused by glycogen branching enzyme deficiency. Accumulation of abnormal glycogen (polyglucosan) causes progressive liver failure, cirrhosis, and death in infancy or childhood. Also affects muscle and nervous system.

An infection of the bone caused by bacteria or fungi. Can occur suddenly (acute) or over long periods (chronic). Requires prompt treatment to prevent permanent bone damage. Most commonly affects long bones and spine.

The most common type of anemia, caused by insufficient iron leading to decreased hemoglobin production. Can result from inadequate dietary intake, blood loss, or malabsorption. Affects all age groups globally.

An autoimmune disorder characterized by isolated low platelet count due to immune-mediated platelet destruction and impaired production. Formerly called idiopathic thrombocytopenic purpura. Acute form common in children, chronic in adults.

A group of metabolic diseases characterized by high blood sugar levels over a prolonged period. Types include Type 1 (autoimmune), Type 2 (insulin resistance), and gestational diabetes. Leading cause of blindness, kidney failure, and amputations.

Cancer that forms in the cells of the breasts. Most common cancer in women worldwide. Can occur in men rarely. Subtypes include ductal carcinoma in situ, invasive ductal carcinoma, and invasive lobular carcinoma. HER2, hormone receptor status important.

Cancer that occurs in the prostate, a small walnut-shaped gland in men that produces seminal fluid. Second most common cancer in men. Most grow slowly; some are aggressive. PSA screening controversial.

A group of inherited disorders affecting connective tissues, primarily skin, joints, and blood vessel walls. Thirteen subtypes with varying severity. Hypermobile type most common; vascular type most dangerous.

Cancer that begins in the lining of the uterus (endometrium). Most common gynecologic cancer in developed countries. Type I (endometrioid) associated with estrogen; Type II (serous) more aggressive.

Cancer that begins in the cells of the bladder, most commonly urothelial carcinoma. Smoking is the leading risk factor. Often presents with painless hematuria.

Cancer that develops in the thyroid gland. Papillary carcinoma most common and most curable. Thyroid nodules common but usually benign. Rising incidence partly due to increased detection.

Cancer that begins in the cervix, almost always caused by persistent HPV infection. One of most preventable cancers through screening and vaccination. Declining in developed countries due to screening.

A highly contagious bacterial skin infection most common in young children. Characterized by red sores that quickly rupture, ooze, and form honey-colored crusts. Caused by Staphylococcus or Streptococcus bacteria.

A fungal infection of the feet, particularly between the toes. Common in people with sweaty feet who wear tight-fitting shoes. Highly contagious and can spread to other parts of body.

A clouding of the normally clear lens of the eye, most commonly due to aging. Leading cause of vision loss worldwide. Develops gradually and affects both eyes, usually one more than the other.

Inflammation of the conjunctiva, the thin clear tissue that lies over the white part of the eye and lines the inside of the eyelid. Can be viral, bacterial, or allergic. Highly contagious in infectious forms.

A genetic condition where a person inherits one sickle cell gene and one normal hemoglobin gene. Usually asymptomatic but can cause complications under extreme conditions. Different from sickle cell disease.

A viral infection of the upper respiratory tract, primarily caused by rhinoviruses. The most frequent infectious disease in humans, with adults averaging 2-3 episodes per year. Self-limiting but highly contagious.

Inflammation of the stomach and intestines caused by viruses (norovirus, rotavirus, adenovirus). Commonly called 'stomach flu.' Highly contagious, causing diarrhea, vomiting, and abdominal cramps. Major cause of morbidity worldwide.

A highly contagious viral disease causing fever, cough, runny nose, conjunctivitis, and characteristic rash. One of the most contagious infectious diseases. Can cause serious complications including pneumonia, encephalitis, and death. Vaccine-preventable.

A highly contagious viral infection causing itchy blister-like rash, fever, and fatigue. Caused by varicella-zoster virus (VZV). Usually mild in children but more severe in adults. Can reactivate later as shingles. Vaccine-preventable.

Non-cancerous enlargement of the prostate gland common in aging men. Causes urinary symptoms including frequency, urgency, weak stream, and incomplete emptying. Very common, affecting about half of men over 50. Not related to prostate cancer.

A contagious skin infestation caused by the Sarcoptes scabiei mite. Causes intense itching and rash as the mites burrow into skin to lay eggs. Spreads through close skin-to-skin contact. Common in crowded conditions and healthcare settings.

Hard deposits of minerals and salts that form inside the kidneys. Can affect any part of the urinary tract. Cause severe pain when passing. Very common, affecting 1 in 11 people. Often recurrent. Types include calcium oxalate, uric acid, struvite, and cystine stones.

A common bacterial infection affecting any part of the urinary system including kidneys, ureters, bladder, and urethra. Most commonly affects the lower urinary tract (bladder and urethra). Women are at greater risk than men. Recurrent UTIs affect 20-30% of women.

The involuntary loss of bladder control, ranging from occasional leakage to complete inability to hold urine. Affects twice as many women as men, especially after pregnancy, childbirth, and menopause. Not a normal part of aging but becomes more common with age.

The consistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance. Affects approximately 50% of men aged 40-70. Often an early indicator of cardiovascular disease. Can significantly impact quality of life and relationships.

A chronic condition causing bladder pressure, bladder pain, and sometimes pelvic pain. Part of a spectrum of painful bladder syndromes. More common in women. Symptoms often mimic UTI but urine cultures are negative. Cause is unknown but may involve bladder lining defects.

A connective tissue disorder characterized by the development of fibrous scar tissue (plaque) inside the penis, causing curved, painful erections. Affects 3-9% of men, most commonly between ages 45-60. Can significantly impact sexual function and psychological well-being.

A collection of fluid in the scrotum around the testicle, causing swelling. Common in newborns (usually resolves within first year) and older men. Typically painless but can cause discomfort due to swelling. Two types: communicating (patent processus vaginalis) and non-communicating.

Enlargement of the veins within the loose bag of skin holding the testicles (scrotum), similar to varicose veins in legs. Occurs in 15% of men, most commonly on left side due to venous anatomy. Leading cause of correctable male infertility.

A surgical emergency caused by twisting of the spermatic cord, cutting off blood supply to the testicle. Most common in adolescent males (ages 12-18) but can occur at any age. Requires immediate treatment within 6 hours to save the testicle. Affects 1 in 4,000 males under 25 annually.

Inflammation of the epididymis, the coiled tube at the back of the testicle that stores and carries sperm. Most common cause of acute scrotal pain in adults. Can be caused by bacterial infection (sexually transmitted or urinary pathogens) or non-infectious inflammation.

Inflammation of the urethra, the tube that carries urine from the bladder out of the body. Most commonly caused by sexually transmitted infections (chlamydia, gonorrhea) but can also be non-infectious. Affects both men and women, though symptoms are more prominent in men.

An anxiety disorder characterized by recurrent unexpected panic attacks—sudden periods of intense fear that reach a peak within minutes. Affects 2-3% of adults annually. Often associated with agoraphobia (fear of situations where escape might be difficult).

A chronic mental health condition characterized by intense, persistent fear of being watched and judged by others. Goes beyond ordinary shyness. Affects approximately 7% of adults. Often begins in childhood or adolescence. Can severely impact social and occupational functioning.

A highly contagious, vaccine-preventable liver infection caused by hepatitis A virus. Transmitted through fecal-oral route, typically via contaminated food/water or close contact. Usually self-limited with full recovery and no chronic infection. Common in areas with poor sanitation.

A liver disease caused by hepatitis E virus, transmitted primarily through contaminated water. Similar to hepatitis A in transmission and course. Most common in South Asia and East Asia. Genotypes 1 and 2 cause large waterborne outbreaks; genotypes 3 and 4 are zoonotic. High mortality in pregnant women (15-25%).

A bulge or ballooning in the wall of the aorta, the body's main artery. Can occur in the chest (thoracic) or abdomen (abdominal). Life-threatening if it ruptures. Often asymptomatic until complications occur. Associated with atherosclerosis, hypertension, and genetic conditions.

Narrowing of the aortic valve opening, restricting blood flow from the heart to the aorta. Most commonly caused by age-related calcification, congenital bicuspid valve, or rheumatic fever. Progressive disease; severe cases require valve replacement.

A condition where the mitral valve doesn't close tightly, causing blood to flow backward into the left atrium when the heart contracts. Can be primary (valve problem) or secondary (heart enlargement). Leads to heart enlargement and heart failure if severe.

Inflammation of the pericardium, the thin sac surrounding the heart. Causes chest pain and can lead to fluid accumulation (pericardial effusion) or heart compression (cardiac tamponade). Often idiopathic but can follow viral infections or autoimmune conditions.

Inflammation of the heart muscle (myocardium) that can weaken the heart and affect its electrical system. Often follows viral infections but can be autoimmune or drug-related. Can cause heart failure, arrhythmias, or sudden cardiac death.

A genetic condition causing abnormal thickening of the heart muscle, particularly the left ventricle. Most common cause of sudden cardiac death in young athletes. Can obstruct blood flow (obstructive HCM) or not (non-obstructive).

Narrowing of peripheral arteries, usually in the legs, due to atherosclerosis. Reduces blood flow to limbs causing pain with walking (claudication). Strong marker for cardiovascular disease elsewhere. Increases risk of heart attack and stroke.

Infection of the inner lining of the heart chambers and valves. Usually caused by bacteria entering the bloodstream. Life-threatening condition requiring prolonged antibiotic therapy and sometimes surgery. Risk increased in those with prosthetic valves or congenital heart disease.

Buildup of abnormal amyloid protein in the heart tissue causing stiffening and restrictive cardiomyopathy. Two main types: ATTR (transthyretin, age-related or hereditary) and AL (light chain, associated with multiple myeloma). Increasingly recognized cause of heart failure with preserved ejection fraction.

A blockage in one of the pulmonary arteries in the lungs, usually caused by blood clots that travel from deep veins in the legs (DVT). Life-threatening condition requiring immediate treatment. Can cause sudden death if massive.

Accumulation of excess fluid in the pleural space between the lungs and chest wall. Can be caused by heart failure, pneumonia, cancer, pulmonary embolism, or liver/kidney disease. Symptoms depend on amount and rate of fluid accumulation.

A pus-filled cavity in the lung surrounded by inflamed tissue, usually caused by bacterial infection. Often follows aspiration pneumonia. Associated with poor dental hygiene, alcoholism, or swallowing disorders. Modern antibiotics have reduced incidence significantly.

Collapsed lung due to air leaking into the space between the lung and chest wall. Can be spontaneous (no obvious cause), traumatic (injury), or tension (life-threatening). Primary spontaneous occurs in tall, thin young men. Requires prompt treatment.

A breathing disorder in obese people where poor breathing leads to too much carbon dioxide and too little oxygen in the blood. Often overlaps with obstructive sleep apnea. Can lead to pulmonary hypertension, heart failure, and early death if untreated.

Cancer of the voice box (larynx), most commonly squamous cell carcinoma. Strongly associated with tobacco and alcohol use. Hoarseness is the most common early symptom. Can affect voice, swallowing, and breathing depending on location.

Cancer arising from the nasopharynx, the area behind the nose and above the back of the throat. Strongly associated with Epstein-Barr virus (EBV), genetic factors, and certain dietary habits (salted fish). Common in Southeast Asia and North Africa.

Also known as delta hepatitis, caused by the hepatitis D virus (HDV) which requires hepatitis B virus to replicate. The most severe form of viral hepatitis with rapid progression to cirrhosis. Occurs as coinfection (with HBV) or superinfection (in chronic HBV).

Progressive form of non-alcoholic fatty liver disease (NAFLD) characterized by liver inflammation and damage in people who drink little or no alcohol. Can progress to cirrhosis, liver failure, and liver cancer. Associated with obesity, diabetes, and metabolic syndrome.

Sudden inflammation of the pancreas, usually mild and self-limiting but can be life-threatening. Most commonly caused by gallstones or alcohol. Presents with severe abdominal pain. Can lead to pancreatic necrosis, organ failure, or pseudocysts.

Inability to fully digest lactose, the sugar in milk and dairy products, due to deficiency of lactase enzyme in the small intestine. Very common worldwide, especially in certain ethnic groups. Not dangerous but can cause uncomfortable symptoms.

Narrowing of the esophagus causing difficulty swallowing (dysphagia). Most commonly caused by chronic acid reflux (GERD) leading to scar tissue formation. Other causes include radiation, eosinophilic esophagitis, cancer, and ingestion of caustic substances.

A cluster of conditions including increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels. Occurring together, they increase risk of heart disease, stroke, and type 2 diabetes. Very common in developed countries.

A group of genetic disorders causing brittle bones that break easily. Caused by defects in type I collagen. Range from mild (few fractures) to severe (lethal in infancy). Also known as brittle bone disease. Can affect teeth, hearing, and connective tissue.

A rare genetic disorder causing episodes of muscle weakness or paralysis triggered by low potassium levels. Episodes often occur during rest after exercise or high-carbohydrate meals. Muscles work normally between attacks. Can lead to permanent weakness over time.

A chronic neurological disorder affecting the brain's ability to control sleep-wake cycles. Characterized by excessive daytime sleepiness and cataplexy (sudden muscle weakness triggered by emotions). Often caused by loss of hypocretin-producing neurons. Onset typically in adolescence.

A neurological disorder causing uncomfortable sensations in the legs and an irresistible urge to move them. Symptoms worse at rest and in the evening/night. Significantly disrupts sleep. Associated with iron deficiency, kidney disease, pregnancy, and certain medications.

One of the most common causes of vertigo, triggered by specific changes in head position. Caused by tiny calcium crystals (canaliths) becoming dislodged in the inner ear. Brief, intense episodes of spinning sensation lasting less than a minute.

A tear in one or more of the four rotator cuff tendons in the shoulder (supraspinatus, infraspinatus, teres minor, subscapularis). Can occur from acute injury or degenerative changes with aging. Causes shoulder pain and weakness, especially with overhead activities.

Narrowing of the spaces within the spine, putting pressure on the spinal cord and nerves. Most commonly affects the lower back (lumbar) and neck (cervical). Causes pain, numbness, and muscle weakness. Usually age-related degenerative changes.

When the soft inner material of a spinal disc in the lower back pushes through the tough outer layer, irritating nearby nerves. Commonly called a slipped or ruptured disc. Most common in ages 30-50. Most improve with conservative treatment within 6 weeks.

Inflammation of the Achilles tendon, the large tendon connecting the calf muscles to the heel bone. Common in runners and athletes who have suddenly increased training intensity. Causes pain and stiffness along the back of the leg near the heel.

Inflammation of the plantar fascia, a thick band of tissue running across the bottom of the foot connecting the heel bone to the toes. Causes stabbing heel pain, especially with first steps in the morning. Most common cause of heel pain.

Persistent or recurrent infection of the kidneys causing progressive scarring and damage. Usually results from repeated acute pyelonephritis, often due to urinary tract obstruction or vesicoureteral reflux. Can lead to chronic kidney disease and end-stage renal disease.

Narrowing of one or both renal arteries reducing blood flow to the kidneys. Causes hypertension that can be difficult to control and can lead to kidney damage. Usually caused by atherosclerosis (older patients) or fibromuscular dysplasia (younger women).

A kidney disorder where the kidneys cannot concentrate urine due to resistance to antidiuretic hormone (ADH/vasopressin). Causes excessive thirst and excretion of large amounts of dilute urine. Can be inherited (genetic) or acquired (lithium, other medications).

A condition characterized by sudden, involuntary contraction of the bladder muscle causing urgency to urinate, often with frequency and nocturia. May or may not involve urge incontinence. Very common, especially with aging, but not a normal part of aging.

Cancer that starts in the kidneys, most commonly renal cell carcinoma (RCC). Often discovered incidentally on imaging. Associated with smoking, obesity, and hypertension. Can be cured if caught early but has poor prognosis if metastatic.

A congenital condition in males where the opening of the urethra is located on the underside of the penis rather than at the tip. One of the most common birth defects of the male genitalia. Varies in severity based on location of urethral opening.

A fluid-filled sac in the epididymis, the coiled tube behind each testicle that stores and carries sperm. Very common and benign. Usually painless and discovered during self-exam. Can vary in size. Different from testicular cancer.

A chronic eye condition where fluid in the eye doesn't drain properly, causing increased pressure that damages the optic nerve. The most common type of glaucoma. Called the 'silent thief of sight' because it causes gradual vision loss without early symptoms.

Clouding of the eye's natural lens that occurs with aging. The most common type of cataract and a leading cause of vision impairment worldwide. Develops gradually over years. Surgery is the only effective treatment and is highly successful.

Inflammation of the eyelids causing red, irritated, itchy eyelids and dandruff-like scales on eyelashes. Very common and chronic condition. Associated with dry eye, meibomian gland dysfunction, and sometimes skin conditions like rosacea or dandruff.

Blood pooling in the anterior chamber of the eye between the cornea and iris, usually due to trauma. Can cause increased eye pressure and vision loss. Medical emergency requiring prompt evaluation and management to prevent complications like glaucoma and corneal staining.

Misalignment of the eyes in adults, either persistent from childhood or newly acquired. Can cause double vision, eye strain, and difficulty with depth perception. New-onset in adults often indicates underlying neurological or medical condition requiring evaluation.

Overproduction of thyroid hormones causing accelerated metabolism. Most commonly caused by Graves' disease, toxic nodular goiter, or thyroiditis. Affects multiple body systems and requires treatment to prevent serious complications like heart problems and osteoporosis.

A rare X-linked genetic disorder caused by mutations in the ABCD1 gene, leading to accumulation of very long-chain fatty acids in the nervous system and adrenal glands. Childhood cerebral form causes progressive neurological deterioration.

Autosomal dominant neurodegenerative disorder. CAG repeat expansion in HTT gene. Choreiform movements, cognitive decline, psychiatric symptoms. Inevitably fatal.

A medical emergency occurring when blood flow to the heart is severely reduced or blocked, causing heart muscle damage. Usually caused by a blood clot forming in a coronary artery already narrowed by atherosclerosis. Time-critical condition requiring immediate treatment to minimize heart damage.

A common bacterial skin infection affecting the deeper layers of skin and subcutaneous tissue. Usually caused by Streptococcus or Staphylococcus bacteria entering through breaks in the skin. Can spread rapidly and become life-threatening if not treated promptly.

A condition where small pouches (diverticula) form and bulge outward through weak spots in the colon wall. Very common in adults over 60 in developed countries. Usually asymptomatic but can lead to diverticulitis (inflammation) or bleeding. Associated with low-fiber Western diet.

A pregnancy complication characterized by high blood pressure and signs of damage to other organ systems, typically liver and kidneys. Usually begins after 20 weeks of pregnancy. Can lead to serious complications for both mother and baby including eclampsia (seizures). Leading cause of maternal and perinatal morbidity worldwide.

A potentially life-threatening condition where a fertilized egg implants and grows outside the main cavity of the uterus, most commonly in a fallopian tube. The pregnancy cannot proceed normally and can cause the fallopian tube to rupture, leading to severe internal bleeding. Requires immediate medical intervention.

A chronic inflammatory lung disease causing obstructed airflow from the lungs. Includes emphysema (destruction of lung air sacs) and chronic bronchitis (inflammation of bronchial tubes). Progressive disease that makes breathing increasingly difficult over time. Primarily caused by smoking.

A condition where bone mineral density is lower than normal but not low enough to be classified as osteoporosis. Considered a precursor to osteoporosis and increases fracture risk compared to normal bone density. Often asymptomatic until a fracture occurs.

A tropical parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. Acquired through contact with contaminated freshwater. Affects over 240 million people worldwide, primarily in Africa. Second most devastating parasitic disease after malaria.

A parasitic disease caused by the nematode worm Onchocerca volvulus, transmitted through the bites of infected blackflies. Leading cause of infectious blindness worldwide. Affects approximately 20-25 million people, primarily in sub-Saharan Africa. WHO goal is elimination by 2030.

A neglected tropical disease caused by filarial worms transmitted by mosquitoes. Damages lymphatic system causing abnormal enlargement of body parts. Affects over 120 million people in 72 countries. WHO goal is elimination by 2030.

A rare inflammatory disease affecting skin and muscles, causing muscle weakness and distinctive skin rash. Belongs to a group of conditions called inflammatory myopathies. Can occur at any age but most common in adults 40-60 and children 5-15. Associated with increased cancer risk in adults.

A rare inflammatory muscle disease causing progressive muscle weakness, particularly in the proximal muscles (shoulders, hips, thighs). Belongs to idiopathic inflammatory myopathies. Affects adults primarily, rare in children. Associated with interstitial lung disease in some cases.

An inflammatory disease causing granulomas (clumps of inflammatory cells) to form in various organs, most commonly the lungs and lymph nodes. Can affect any organ system. Cause unknown. Affects approximately 1-40 per 100,000 people, more common in African Americans and Scandinavians. Often remits spontaneously.

An autoimmune disorder characterized by recurrent blood clots (thrombosis), pregnancy complications, and the presence of antiphospholipid antibodies. Can occur alone (primary) or with other autoimmune diseases (secondary, usually lupus). Affects approximately 1-5 per 100,000 people.

An inflammatory disease of blood vessels, most commonly affecting the arteries in the head, particularly the temples. Most common form of vasculitis in adults over 50. Can cause sudden blindness if untreated. Associated with polymyalgia rheumatica in 50% of cases. Affects approximately 0.5-27 per 100,000 people.

A condition characterized by an abnormal increase in heart rate upon standing, without a drop in blood pressure. Part of a group of disorders called dysautonomia. Affects primarily women aged 15-50. Can be debilitating. Affects approximately 1-3 million people in the US alone.

A genetic disorder causing noncancerous (benign) tumors to develop in many parts of the body, particularly the brain, skin, kidneys, heart, and lungs. Affects approximately 1 in 6,000 people. TSC1 or TSC2 gene mutations cause overactivation of mTOR pathway.

A rare congenital neurological and skin disorder characterized by a facial port-wine birthmark, neurological abnormalities including seizures, and eye problems such as glaucoma. Caused by somatic mutation in GNAQ gene. Affects approximately 1 in 20,000-50,000 people.

A rare, usually fatal neurological disorder causing destruction of white matter in the brain. Characterized by abnormal protein (GFAP) deposits called Rosenthal fibers. Most common form is infantile, but juvenile and adult forms exist. Affects approximately 1 in 2.7 million people. No cure available.

A rare, inherited disorder destroying the protective coating (myelin) of nerve cells in the brain and throughout the nervous system. Caused by deficiency of galactocerebrosidase enzyme. Most common form is infantile with rapid progression. Affects approximately 1 in 100,000 people.

A severe, often fatal hemorrhagic fever caused by Marburg virus, related to Ebola virus. Transmitted through contact with infected animals (primarily fruit bats) or person-to-person through bodily fluids. First recognized in 1967 in Germany and Yugoslavia. Case fatality rate 23-90%.

A viral respiratory illness caused by Middle East Respiratory Syndrome Coronavirus (MERS-CoV). First reported in Saudi Arabia in 2012. Transmitted from camels to humans and person-to-person in close contact. Case fatality rate approximately 35%. Most cases in Arabian Peninsula.

Inflammation of the stomach and intestines causing diarrhea, vomiting, and abdominal cramps. Usually caused by viral, bacterial, or parasitic infections. Common worldwide and especially dangerous in young children and elderly.

An allergic response causing sneezing, runny nose, and itchy eyes when exposed to allergens like pollen, dust mites, or pet dander. One of the most common allergic conditions worldwide affecting quality of life.

An abnormal heart rhythm characterized by rapid, regular atrial contractions at around 250-350 beats per minute. Similar to atrial fibrillation but with organized electrical activity. Increases stroke risk.

A condition where small bulging pouches (diverticula) develop in the digestive tract, typically the colon. Includes diverticulosis (presence of pouches) and diverticulitis (inflammation/infection). Very common in Western populations.

A serious brain injury where blood accumulates between the skull and the dura mater, usually due to traumatic head injury. Often involves arterial bleeding and is a medical emergency requiring immediate surgery.

Swollen veins in the lower rectum and anus, similar to varicose veins. Very common condition affecting about half of adults over age 50. Can cause pain, itching, and bleeding.

A condition characterized by abnormally low blood glucose levels (below 70 mg/dL). Can occur in diabetics due to medication or in non-diabetics due to various medical conditions. Requires immediate treatment.

Inflammation of the voice box (larynx) causing hoarseness or voice loss. Usually temporary and caused by viral infection, overuse, or irritation. Can be acute or chronic.

A chronic inflammatory skin condition causing patchy, discolored, thin skin, typically in genital and perianal areas. More common in postmenopausal women but affects all ages and genders. Associated with increased skin cancer risk.

A tumor that arises from the meninges, the membranes that surround the brain and spinal cord. Usually benign and slow-growing, but can become atypical or malignant. Most common type of primary brain tumor.

A fungal infection of the toenails or fingernails causing discoloration, thickening, and crumbling of the nail. Very common condition, especially in older adults. Can be difficult to treat.

Inflammation of the patellar tendon connecting the kneecap to the shinbone. Common in athletes who jump frequently. Causes pain below the kneecap and can lead to tendon degeneration if untreated.

Damage to the peripheral nerves causing weakness, numbness, and pain, typically in hands and feet. Can result from diabetes, infections, injuries, or toxins. Affects millions worldwide.

Common benign skin growths that appear as waxy brown, black, or tan spots. Often called 'barnacles of aging.' Very common in older adults. Not contagious or premalignant but can be cosmetically concerning.

Bleeding into the subarachnoid space between the brain and surrounding membrane. Usually caused by ruptured cerebral aneurysm. Medical emergency with high mortality. Classic 'thunderclap' headache.

The most common form of focal epilepsy originating in the temporal lobe. Often associated with hippocampal sclerosis. Causes seizures with distinctive features like déjà vu, strange smells, or autonomic symptoms.

Inability to empty the bladder completely. Can be acute (sudden, painful) or chronic (gradual, painless). Caused by obstruction, nerve problems, or medications. Requires prompt treatment to prevent kidney damage.

Benign growths on both vocal cords, usually at the midpoint, caused by vocal abuse or overuse. Also called singer's or screamer's nodules. Most common in children and professional voice users.

A complex, chronic disorder characterized by extreme fatigue that cannot be explained by any underlying medical condition and does not improve with rest. Associated with post-exertional malaise, cognitive impairment, and orthostatic intolerance.

An infection of the female reproductive organs, usually caused by sexually transmitted bacteria spreading from the vagina to uterus, fallopian tubes, or ovaries. Affects approximately 4.4% of women of reproductive age. Leading preventable cause of infertility and ectopic pregnancy.

Inflammation of the vagina that can result in discharge, itching and pain. The most common types are bacterial vaginosis, yeast infections, and trichomoniasis. Affects millions of women annually and is one of the most common reasons for gynecologic visits.

A chronic pain condition affecting the vulva, characterized by burning, stinging, irritation, or rawness. Affects up to 16% of women. The cause is unknown and diagnosis is often delayed. Significantly impacts quality of life and sexual function.

Abnormally heavy or prolonged menstrual bleeding affecting up to 25% of women. Can cause anemia and significantly impact quality of life. Often caused by hormonal imbalances, uterine fibroids, or bleeding disorders.

A combination of physical and emotional symptoms that occur 1-2 weeks before menstruation. Affects up to 90% of women of reproductive age. Severe form (PMDD) affects 3-8% and causes significant functional impairment.

Persistent or recurrent genital pain that occurs just before, during, or after intercourse. Affects up to 20% of women. Can have physical or psychological causes. Significantly impacts sexual health and relationships.