X-linked agammaglobulinemia (XLA) (
MIM: 300755) is an inherited
immunodeficiency caused by mutation in the Bruton's tyrosine kinase (Btk) gene
Xq21.33-q22). It leads to failure in development of mature B lymphocytes and a
reduced Ig production. Patients typically present in early childhood with
recurrent infections. XLA is treated by infusion of human antibody.