Introduction:X-linked agammaglobulinemia (XLA), or Bruton agammaglobulinemia, is an inherited immunodeficiency disease that caused by variations of Bruton tyrosine kinase gene (BTK). In 1952 Bruton, described the disease for the first time, for whom the gene is named. In the process of maturating B cells BTK is needed ,that helps differentiating process.The BTK gene is located on the long arm of the X chromosome, within the Xq21.3–Xq22 region, and extends over approximately 37.5 kb. It contains 19 exons that encode a 659–amino-acid cytoplasmic tyrosine kinase. In addition, a missense variant affecting the TH domain of BTK has also been reported.(1)In the absence of BTK, B lymphocytes do not differentiate or mature,that this absence of mature B cell leads to impairment antibody-producing. This disorder also leads to poorly developing of reticuloendothelial and lymphoid organs as a consequence. Organs like as spleen,tonsils,adenoids,and ofcourse lymph nodes may all reduce in size or even absent.(1)Cloning of the proto-oncogene that encodes BTK and clarification of its genomic structure have made it possible to thoroughly investigate the contribution of BTK and associated signaling pathways to B-cell maturation. (2,3)Because of x_linked recessive inheritance approximately 85% of the affected subjects are male (4). Carrier females show no symptoms but because of mode of inheritance of the gene have a 50% chance for transmission to each of their sons (4).The prevalence of the disease ranges from 1 in 10,000 to 1 in 50,000 (1).Interestingly, half of the patients are diagnosed within the first year, while the rest may not be diagnosed until the age of 90.(4). The diagnosis is supported by observing of lymphoid underdevelopment, such as markedly small or absent tonsils and non-palpable lymph nodes, together with a total immunoglobulin concentration typically below 100 mg/dL. In addition, isohemagglutinins and vaccine-induced antibody responses are significantly reduced in affected individuals. One of the best tests in diagnosing the Bruton disease is Flow cytometry (5).And about neurologic manifestation of this disease, it seems that it is not a common manifestation, just few case reports have been reported conditions like as, progressive neurodegenerative encephalopathy, enteroviral infection, or some movement disorder, but here we reported a case of XLA due to Bruton tyrosine kinase gene variant with ataxia.
