Abstract: Objective　To explore the clinical characteristics and gene mutation types of severe combined immunodeficiency (SCID) caused by gene mutation of interleukin-2 receptor common γ-chain (IL2RG). Method　The clinical data of SCID caused by IL2RG gene mutation in a child were retrospectively analyzed. Results　A 48-day-old male infant presented multiple infections, leukopenia and poor efficacy of antibiotics in the early postnatal period. The infant had IgG 2.93 g/L, IgA < 0.07 g/L, IgM 0.16 g/L, C3 0.67 g/L and C4 0.13 g/L, the proportion of CD3+CD4+ T lymphocytes at 0.03%, CD3+CD8+ T lymphocytes 0.1%, CD3－/CD16+CD56+ NK cells 2.6% and CD3－CD19+ B lymphocytes 96.76%. Secondgeneration gene sequencing showed that the IL2RG gene (chrX: 70328484, HG19) had a hemizygous variation of c.816_819 delGATT (p.L273fs*20), which was a rare frame shift mutation. The software predicted that the mutation would lead to an early termination codon in protein synthesis, which was a type-1 pathogenic mutation. The mother of the infant was in a heterozygous state, the father did not have this mutation, and the mother's sister also had this heterozygous mutation. Conclusion　We found a case of SCID caused by mutation of IL2RG gene [c.816-819delGATT (p.L273fs*20)]. Gene sequencing analysis combined with sex identification can screen carriers in proband families and make prenatal diagnosis.

Key words: 　severe combined immunodeficiency;　IL2RG gene;　mutation