A nonsense variant of reactivation gene-1 leads to Omenn syndrome in a Pakistani family

OBJECTIVE: To conduct clinical and genetic analysis in a patient with severe combined immunodeficiency disease (SCID). METHODS: A 3.5-year-old female patient with chronic diarrhea, fever, and failure to thrive was examined at the Pakistan Institute of Medical Sciences, Islamabad. Ethical approval was obtained, and informed consent was secured for genetic studies. Flow cytometry was performed on blood samples to evaluate T, B, and NK cell concentrations. Genomic DNA was extracted from peripheral blood samples of the patient, her mother, and healthy siblings. Sanger sequencing of the RAG1 gene was conducted, followed by mutational analysis using BioEdit and bioinformatics tools for pathogenicity assessment. RESULTS: The proband, the youngest girl born to first-cousin parents presented with intractable diarrhea with failure to thrive and skin and nappy rashes on clinical evaluation. The immunological assessment revealed total absence of B and T lymphocytes, normal NK cells (47% with 85% CD16 and CD56 respectively: No CD4, CD8 and CD19), and significant hypogammaglobulinemia (IgG;165 mg/dl, IgM; 9 mg/dl, IgA;8 mg/dl), while normal level of IgE (2 mg/dl). On the other hand, targeted Sanger sequencing of RAG1 exon 2 region revealed a new homozygous deleterious mutation (NM_000448.2: c.2876 G>A; p.Trp959*) in the RAG1 gene resulting in complete loss of function due to the production of truncated protein. CONCLUSION: We identified a potentially pathogenic nonsense mutation in the RAG1 gene (c.2876 G>A; p.Trp959*) in a child with SCID. This finding emphasizes the significance of early detection for timely treatment and genetic counseling.