Bruton's tyrosine kinase gene mutations in Turkish patients with X-linked agammaglobulinemia from a single center: Novel mutations in βTK gene

Objective: X-linked agammaglobulinemia (XLA) is caused by a mutation in the Bruton's tyrosine kinase gene and is characterized by a delay in the maturation and differentiation of B lymphocytes. Patients with XLA have either absent or very low levels of circulating mature B cells (<1%), plasma cells, and immunoglobulins of all isotypes. Recurrent bacterial infections are prevalent in patients with XLA. The absence of B cells, agammaglobulinemia and the clinical features of XLA are similar to autosomal recessive forms such as μ heavy chain, λ5, Igα, Igβ and a BLNK gene defects. The aim of this study was to diagnose Turkish patients with suspected XLA by using BTK mutation analysis. Material and Methods: Fourteen male children recruited from 13 different families that were diagnosed with suspected XLA based on recurrent bacterial infections, decreased B cell count in the peripheral blood and hypogammaglobulinemia were included in the study. Clinical and demographic features of patients, serum immunoglobulin levels, peripheral blood B cell counts and BTK gene mutations were reviewed retrospectively. Patients were examined for BTK mutations by polymerase chain reaction. Results: Three of 14 patients were the children of consanguineous marriages and 3 families had a history of immune deficiencies. Most of the patients presented with infections, primarily pneumonia. BTK mutation resulting in XLA was detected in 10 patients. Eight patients had previously been diagnosed and 2 patients had novel mutations. Conclusion: Mutation analysis must be done to differentiate XLA from other autosomal recessive forms such as μ heavy chain, λ5, Igα, Igβ and a BLNK gene defects and this is necessary to design genetic counseling for newly diagnosed patients.

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