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.

• 1Genetic testing
• 2Clinical evaluation
• 3Family history assessment
• 4Specialized laboratory tests
• 5Imaging studies
• 6Biopsy (if applicable)

Good with Ig replacement. Chronic lung disease common. Enteroviral infections can be severe. Life expectancy improving with modern care.

• Genetic counseling
• Carrier screening
• Prenatal diagnosis
• Preimplantation genetic diagnosis
• Family planning