Agammaglobulinemia associated to nasal polyposis due to a hypomorphic RAG1 mutation in a 12 years old boy

Abstract

Recombination-activating gene (RAG) 1 and 2 mutations in humans cause T^- B^- NK⁺ SCID and Omenn syndrome, but milder phenotypes associated with residual protein activity have been recently described. We report a male patient with a diagnosis of common variable immunodeficiency (CVID) born from non-consanguineous parents, whose immunological phenotype was characterized by severe reduction of B cells and agammaglobulinemia for which several candidate genes were excluded by targeted Sanger sequencing. Next Generation Sequencing revealed two compound heterozygous mutations in the RAG1 gene: the previously described p.R624H, and the novel p.Y728H mutation, as well as the known polymorphism p.H249R. This case reinforces the notion of large phenotypic spectrum in RAG deficiency and opens questions on the management and follow-up of these patients.

Keywords: EBV viremia; Humoral defect; Hypomorphic mutation; RAG1.