Tehran University of Medical Sciences Immunology and Genetics Journal 2645-4831 4 4 2021 12 22 203 210 Salar Pashangzadeh Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Science, Tehran, Iran Reza Yazdani Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Science, Tehran, Iran Samaneh Delavari Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Science, Tehran, Iran Hassan Abolhassani Division of Allergy and Clinical Immunology, Department of Pediatrics, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran Nima Parvaneh Division of Clinical Immunology, Department of Biosciences and Nutrition, Karolinska Institute, Stockholm, Sweden 2022 03 01 2022 12 02 T and B lymphocytes development and function are highly dependent on Recombination Activating Genes (RAG) 1 and 2. RAG mutations result in different degrees of T and B cell impaired function, broad clinical manifestations, and immunological manifestations. Pathogenic mutations cause severe combined immunodeficiency (SCID) phenotype, while hypomorphic mutations are responsible for leaky or partial SCID. Here, we described a 4-year-old girl who had a persistent diarrhea, recurrent infection, and vomiting. Although physicians were suspicious about autoimmune enteropathy, her molecular report showed a homozygous and novel RAG2 mutation in its core domain. The number of CD4 T cells and IgA level were lower than normal ranges. Lack of IgA brought about different GI complications. Our patient died finally because of liver and gallbladder failure. https://igj.tums.ac.ir/index.php/igj/article/view/93 https://igj.tums.ac.ir/index.php/igj/article/download/93/88