immunoglobulin A deficiency type 2
immunoglobulin A deficiency type 2The most common form (OMIM:609529) of primary immunodeficiency, which occurs in 1 in 600 individuals. Patients with symptomatic IGAD often have deficiency of IgG subclasses, reduced antibody response to carbohydrate antigens (e.g., pneumococcal polysaccharide vaccine), suffer recurrent sinopulmonary and GI tract infections, and have an increased incidence of autoimmune disorders and cancer. Some patients with IGAD have impaired isotype class switching to IgA; others have a post-switch defect. IGAD and CVID may coexist in the same patient or family, suggesting a common aetiology.
Defects in TNFRSF13B, which encodes a lymphocyte-specific TNF receptor that plays a key role in humoral immunity, cause immunoglobulin A (IgA) deficiency type 2.