RESUMO
The X-linked hyper IgM syndrome is a primary immunodeficiency disorder (PID) due to mutations in the CD40LG gene. Hyper IgM syndrome is characterized by the absence or decreased levels of IgG and IgA and normal or elevated IgM levels in serum. Affected patients become susceptible to infections such as pneumonia, diarrhea, and skin ulcer types. Hematopoietic stem cell transplantation is the only treatment currently available and ideally performed before the age of 10 years. Early, accurate diagnosis will contribute to the effective treatment for patients with hyper IgM. The patients from different Vietnamese families who have been diagnosed with hyper IgM at The Allergy, Immunology and Rheumatology Department, Vietnam National Hospital Pediatrics, were performed a genetic analysis using whole exome sequencing. The mutations were confirmed by the Sanger sequencing method in patients and their families. The influence of the mutations was predicted with the in silico analysis tools: PROVEAN, SIFT, PolyPhen-2, and MutationTaster. In this study, two novel mutations (p.Thr254fs and p.Leu138Phe) in the CD40LG gene were found in Vietnamese patients with X-linked hyper IgM syndrome. Our results contribute to the general understanding of the etiology of the disease and can help diagnose the different forms of PID.