The non-syndromic form of a primary immunodeficiency disease characterised by deficient gamma globulins and associated predisposition to frequent and recurrent infections from infancy. Two forms have been described: X-linked represents approximately 85% of the affected patients, and autosomal which includes recessive and dominant cases but is far less frequent. The clinical signs of the two forms are very similar and include recurrent bacterial infections, diarrhoea and skin infections with onset in infancy. Defects in B lymphocyte development and maturation appear to underlie agammaglobulinaemia. Mutations in seven genes have been reported to be related to IA: BTK (Xq21.33-q22), BLNK (10q23.2-q23.33), CD79A (19q13.2), CD79B (17q23), IGHM(14q32.33), IGLL1 (22q11.23), PIK3R1 (5q13.1) and TCF3 (19p13.3). [from
SNOMEDCT_US]