The inability in humans to synthesize certain immunoglobulins. The most common form is inherited as an X-linked recessive trait, which is symbolized XLA (X-linked agammaglobulinemia) in the early literature. When O. C. Bruton described the condition in 1952, it was the first hereditary immune disease to be reported. The disease is now known to be caused by mutations in a gene at Xq21.3–q22. The gene is 36,740 bp long, and it encodes a protein containing 659 amino acids. The protein is a tyrosine kinase that has been named in Bruton's honor, and the gene is now symbolized BTK, for its product, the Bruton tyrosine kinase. The enzyme is a key regulator in the development of B lymphocytes. Boys with XLA lack circulating B cells. The bone marrow contains pre-B cells, but they are unable to mature. See antibody.
Subjects: Genetics and Genomics.