X-linked agammaglobulinemia (XLA): A genetic tyrosine kinase (Btk) disease
X-linked agammaglobulinemia is a heritable immunodeficiency disease caused by a differentiation abnormality, resulting in the virtual absence of B lymphocytes and plasma cells, The affected gene encodes a cytoplasmic protein tyrosine kinase, Bruton's agammaglobulinemia tyrosine kinase, designated Btk, Btk and the other family members, Tec, Itk and Bmx, contain five regions, four of which are commo