Abstract
BackgroundX-linked agammaglobulinaemia (XLA) is a rare immunodeficiency disease for which recurrent severe infection is the major clinical symptom. BTK is the main causative gene, with X chromosome recessive inheritance. However, the mutations reported to date do not fully explain the disorder.MethodsWe detected the percentage of CD19+ B cells and serum immunoglobulin (IgG, IgA, and IgM) levels by flow cytometry and rate scatter immunoturbidimetry, and investigated the BTK mutation profile in 22 XLA patients using Sanger sequencing and real-time PCR .ResultsWe evaluated the clinical symptoms of 22 XLA patients and investigated genetic mutations present, identifying six novel mutations in the BTK gene: 2 missense mutations (c.23G > T and c.112 T > C), 2 frameshift mutations (c.522_523insC and c.1060delA), 1 large deletion (deletion of exon 2 to 5), and 1 splice-site mutation (c.1631 + 2 T > C). Prenatal diagnoses were performed in six families (F10, F11, F15, F18, F20 and F21), with the following results: the male fetus in Family 10 (F10) did not carry the c.922_923delGA mutation; the male fetus in Family 15 (F15) did not carry the c.1631 + 1G > T splicing mutation; the female fetus in Family 20 (F20) did not carry the c.1931 T > C mutation; the female fetus in Family 21 (F21) did not carry the large deletion mutation. Hence, these four fetuses are not likely to develop XLA. Male fetuses with c.1060delA and c.1684C > T mutations were identified in Family 11 and Family 18, respectively. The pregnant woman in F18 chose to terminate the pregnancy, whereas the pregnant woman in F11 chose to continue the pregnancy.ConclusionWe confirmed the diagnosis of 22 XLA patients from 22 unrelated families and detected six new pathogenic mutations. Prenatal diagnosis was performed in six families. Early genetic diagnosis and routine lifelong immunoglobulin replacement therapy can prevent and treat infections in XLA children, saving their lives.
Highlights
X-linked agammaglobulinaemia (XLA) is a rare immunodeficiency disease for which recurrent severe infection is the major clinical symptom
The protein encoded by the gene is a cytoplasmic tyrosine kinase that contains five different functional domains: pleckstrin homology (PH), Tec homology (TH), Src homology 3 (SH3), SH2, and kinase (TK) domains [5]
Clinical characteristics Twenty-two families were enrolled in this study
Summary
X-linked agammaglobulinaemia (XLA) is a rare immunodeficiency disease for which recurrent severe infection is the major clinical symptom. BTK is the main causative gene, with X chromosome recessive inheritance. X-linked agammaglobulinaemia (XLA, OMIM: 300755) is a rare immunodeficiency disease caused by defective B cell development and extremely low numbers of mature B cells [1]. The main clinical symptom of XLA is recurrent severe infection [2]. The estimated incidence of XLA is approximately 1:250,000, and the causative mutations are located in the Bruton’s tyrosine kinase (BTK) gene [3, 4]. The protein encoded by the gene is a cytoplasmic tyrosine kinase that contains five different functional domains: pleckstrin homology (PH), Tec homology (TH), Src homology 3 (SH3), SH2, and kinase (TK) domains [5]. BTK participates in B cell receptor (BCR) engagement by antigens and induces a range of protein interactions as well as recruitment of signaling molecules, resulting in B cell survival, proliferation and differentiation and the production of antibodies [8]
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