Germline Homozygous RAG1 Missense Variant Associated With Epstein-Barr Virus Negative Childhood Burkitt Lymphoma: A Case Report.

The recombination activating gene 1 (RAG1) is essential for V(D)J recombination and lymphocyte development. While biallelic null RAG1 mutations cause severe combined immunodeficiency (SCID), hypomorphic variants have increasingly been associated with immune dysregulation and hematologic malignancies. This study aimed to present a pediatric case of Epstein-Barr virus (EBV)-negative Burkitt lymphoma carrying a novel homozygous RAG1 variant and to discuss its potential association with immune function and malignancy risk. A 9-year-old Turkish male from a consanguineous family was evaluated for hereditary cancer predisposition. Clinical, immunologic, and genetic assessments were performed, including whole-exome sequencing (WES), Sanger validation, and mRNA expression analysis. The patient presented with cervical lymphadenopathy and was diagnosed with EBV-negative Burkitt lymphoma; he had no recurrent infections, abnormal vaccine reactions, or SCID-related features. Immunologic testing, including lymphocyte subsets and immunoglobulin levels, was within normal limits. WES identified a homozygous RAG1 variant (NM_000448.2:c.460C>T; p.Leu154Phe), predicted to be deleterious and absent from population databases. Both the patient and his healthy dizygotic twin were homozygous, while parents were heterozygous carriers. RAG1 mRNA expression was reduced in heterozygotes but similar in homozygous and wild-type individuals; enzymatic activity was not assessed. The patient responded to chemotherapy and remains in remission under follow-up. In conclusion, this case expands the phenotypic spectrum of hypomorphic RAG1 variants to include EBV-negative Burkitt lymphoma without overt immunodeficiency, suggesting a possible link between partial RAG1 dysfunction and pediatric lymphoma susceptibility.