Primary agammaglobulinemia is either an X-linked recessive or an autosmal recessive/dominant inherited immunodeficiency characterized by very low or absent serum antibodies and low or absent circulating B cells due to early blockade of B cell development. Affected individuals develop severe infections in the first few years of life.
The most common form of primary agammaglobulinemia is X-linked agammaglobulinemia (AGMX1, XLA; 300755), also known as Bruton disease, which is caused by a mutation in the BTK gene (300300). AGMX1 accounts for 85 to 95% of male patients with the characteristic findings (Ferrari et al., 2007).
An autosomal recessive inheritance in agammaglobulinemias results in a phenotype similar to that seen in the X-linked form. This phenoytp has been observed in a small number of families and accounts for up to 15% of patients with agammaglobulinemia (Ferrari et al., 2007).