Genetic Detection,Laboratory and Clinical Analysis of X-linked Severe Combined Immunodeficiency Caused by the c.675 C＞A Mutation of IL-2RG Gene in Children
Objective To investigate the molecular genetic characteristics and clinical characteristics of severe combined immunodeficiency(SCID)in children caused by a novel mutation of interleukin 2 receptor gamma IL-2RG gene.Methods The clinical data,laboratory results and genetic testing data of a child with SCID admitted to the Department of Children's Hematology of Northwest Women and Children's Hospital were analyzed.Results A two-month-old male infant was admitted to the hospital for treatment due to recurrent infections after birth.The child's blood routine results showed that the total number of white blood cells was normal,but lymphocytes were decreased.The lymphocyte subpopulation results showed a significant decrease in the proportion of total T(CD3+),helper T(CD3+CD4+),killer T(CD3+CD8+),and NK(CD3-CD16+CD56+)lymphocytes,while the proportion of B(CD3-CD19+)lymphocytes were increased.The immunoglobulin levels showed a significant decrease in IgG,and IgM and IgA were below the lower detection limit.The patient's cytokine levels did not significantly increase during infection.In the last three generations of the mother's family,9 males died of infection within one year after birth.The whole exome sequencing results of the core family revealed a semi zygous new missense mutation[c.675 C＞A,p.S225R(p.Ser225Arg)]in the IL-2RG gene on the X chromosome(chrX:70329160)of the patient,and the mother was a carrier.Based on the above evidence,the child was diagnosed with X-SCID.Subsequently,intravenous immunoglobulin was injected monthly,and routine antibiotics and antiviral drugs were taken to prevent infection,preparing for hematopoietic stem cell transplantation.Because the child was vaccinated with BCG after birth,the child developed disseminated BCG disease at the age of 6 months.After treatment,hematopoietic stem cell transplantation was performed.Conclusion The immune function of the X-SCID patient was severely compromised,which endangered the patient's life,and vaccination with live vaccines may lead to severe infections.This study found that the c.675 C＞A mutation of the IL-2RG gene was a novel pathogenic variation of the genetic cause of X-SCID,expanding the mutation spectrum of the X-SCID pathogenic gene IL-2RG.
IL-2RG geneX-linked severe combined immunodeficiencyimmunodeficiency
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