Case Report and literature review: X-linked severe combined immunodeficiency complicated by Talaromyces marneffei infection caused by a novel pathogenic IL2RG mutation

Background X-linked severe combined immunodeficiency (X-SCID), caused by mutations in the gamma-chain gene of the interleukin-2 receptor ( IL2RG ), is a prevalent form of SCID characterized by recurrent and fatal opportunistic infections that occur early in life. Talaromyces marneffei ( T. marneffei ) infection rarely occurs in children and has a high mortality rate. Case presentation The patient was a 7-month-old male infant who presented with recurrent cough, fever, and hepatosplenomegaly. Lymphocyte subset analysis confirmed the presence of T-B + natural killer immunodeficiency, and blood culture was positive for T. marneffei. Whole-exome sequencing revealed a novel microdeletion insertion mutation (c.818_819delins A (p. Ile273Lys fsTer21) in IL2RG , resulting in a rare shift in the amino acid sequence of the coding protein. The child was diagnosed with X-SCID due to a novel IL2RG mutation, which was further complicated by T. marneffei infection. Despite receiving systemic anti-infection treatment, the patient died 3 days after discharge. To the best of our knowledge, this novel IL2RG mutation has not been reported previously. Conclusions For early-onset T. marneffei infection, clinicians must maintain a high index of suspicion for underlying inborn errors of immunity, and definitive diagnosis hinges on genetic testing.