A novel Bruton’s tyrosine kinase gene (BTK) missense mutation in a Chinese family with X-linked agammaglobulinemia

BACKGROUND: X-linked agammaglobulinemia (XLA) is a rare inherited disease characterized by recurrent bacterial infections, a paucity or absence of peripheral lymphoid tissue, an absence of circulating B cells, and marked depression of serum IgG, IgA, and IgM. Germline mutation of the BTK gene has been identified as a cause of XLA. These mutations cause defects in early B cell development. CASE PRESENTATION: In this study, we report a variant form of XLA with partial B cell function that results from a missense mutation (c.1117C > G) in exon 13 of the BTK gene. A genetic analysis of the family revealed an affected male sibling with a c.1117C > G mutation. He was observed with low level of serum immunoglobulin and CD19+ B cell and received the IVIG replacement therapy regularly in follow up. Four female carriers were found. CONCLUSION: BTK mutation analysis is necessary in the diagnosis of XLA and may be used for subsequent genetic counseling, carrier detection and prenatal diagnosis.