The protein encoded by this gene plays a crucial role in B-cell development. Mutations in this gene cause X-linked agammaglobulinemia type 1, which is an immunodeficiency characterized by the failure to produce mature B lymphocytes, and associated with a failure of Ig heavy chain rearrangement. Alternative splicing results in multiple transcript variants encoding different isoforms.,AGMX1,AT,ATK,BPK,IMD1,PSCTK1,XLA,BTK,Signal Transduction,Kinase,Tyrosine kinases,Cell Biology & Developmental Biology,Apoptosis,Immunology & Inflammation,B Cell Receptor Signaling Pathway,Toll-like Receptor Signaling Pathway,Cell Intrinsic Innate Immunity Signaling Pathway,TLR Signaling,BTK