RAG1 and severe combined immunodeficiency: RAG1/2-deficient patients present with a broad spectrum of clinical manifestations that range from severe combined immunodeficiency (SCID) caused by biallelic null mutations (<5% recombinase activity) to atypical SCID (AS), delayed-onset combined immunodeficiency with granulomas and/or autoimmunity (CID-G/AI) and Omenn Syndrome (OS), and the latter being OS is caused by hypomorphic RAG variants that support residual (5%–30%) recombinase activity (Villa et al., 2001; Delmonte et al., 2018; Villa and Notarangelo, 2019; Delmonte et al., 2020).