Isolated Agammaglobulinemia
Isolated agammaglobulinemia (IA) is the non-syndromic form of agammaglobulinemia, a primary immunodeficiency disease, and is characterized by deficient gamma globulins and associated predisposition to frequent and recurrent infections from infancy.
Epidemiology
Prevalence is estimated to be about 1/250,000 to 1/500/000. Isolated agammaglobulinemia has been reported worldwide in all ethnic groups.
Clinical description
Two forms of IA have been described based on the pattern of inheritance of the genetic defects underlying the disorder: X-linked agammaglobulinemia (XLA) which represents approximately 85% of the affected patients, and autosomal agammaglobulinemia (see these terms) 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 (otitis media, pneumonia, and sinusitis), diarrhea and skin infections with onset in infancy. Late-onset agammaglobulinemia is known as common variable immunodeficiency (CVID; see this term).
Etiology
Defects in B lymphocyte development and maturation appear to underlie agammaglobulinemia. 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).
Genetic counseling
X-linked, autosomal recessive and autosomal dominant cases are reported.