Ommen syndrome, namely impaired V(D)J recombination due to mutations in RAG1 and RAG2,92, 93, 94 and defective DNA repair after V(D)J recombination by mutations in DCLRE1C/ARTEMIS95 cause SCID characterized by erythroderma, desquamation, alopecia, eosinophilia, hepatosplenomegaly, elevated serum IgE levels, and often, colitis.96 Moreover, defects in DNA ligase 4 (LIG4) encoding an ATP‐dependent DNA ligase that joins double stranded breaks during non‐homologous end joining pathway, and is essential for V(D)J recombination, can cause SCID, and can develop IBD.92 Here, RAG1 is linked to severe combined immunodeficiency.