Bruton agammaglobulinemia tyrosine kinase: A genetic type of immunodeficiency characterized by failure to produce mature B lymphocytes and gamma globulin, due to mutation (change) in the agammaglobulinemia tyrosine kinase gene situated on the X chromosome (in the region Xq21.3-q22). The disorder is inherited as an X-linked recessive trait.
Patients are males with absent or minimal lymphoid tissue (for example, with little or no tonsils and adenoids) who are particularly prone to bacterial but not viral infections. Although patients have recurrent bacterial infections, they generally have a normal response to viral infection, because cell-mediated immunity is intact.
A notable exception is the usually fatal echovirus-induced meningoencephalitis often associated with a "dermatomyositis-like" syndrome. A clinical picture resembling rheumatoid arthritis develops in many patients.
Before the advent of antibiotics, death usually occurred in the first decade. Treatment today is with regular IV gamma globulin and prophylactic and therapeutic antibiotics. The prognosis is now markedly improved.