X-linked hyper IgM syndrome: clinical, immunological and molecular features in patients from India

X-linked hyper-IgM (XHIM) is a primary immunodeficiency disorder characterized by recurrent infections, low serum IgG and IgA and normal or elevated IgM. It results from mutations in the CD40 ligand (CD40L) gene. Confirmation of diagnosis with identification of underlying molecular defect is important for the initiation of appropriate therapeutic interventions, including immunoglobulin replacement, antibiotics and bone marrow transplantation.

To investigate the molecular basis of XHIM, we evaluated 7 patients with suspected XHIM and abnormal CD40L expression on activated CD4(+) T lymphocytes. The entire coding region and intronic splice sites of the CD40L gene were sequenced from the genomic DNA of the patients.

7 mutations; 3 nonsense (c.172delA, c.A229T, c.C478T), 1 missense (c.A506G) and 3 splice sites [c.346+2(T→C), c.289-1(G→C), c.346+1(G→T)] were identified, out of which 5 were novel.

A wide heterogeneity in the nature of mutations has been observed in Indian XHIM patients in the present study. Identification of mutations in this rare disorder will help in genetic diagnosis in affected families which could be further useful in prenatal diagnosis.