Interestingly, we found three novel mutations in the RAG1 gene and two in RAG2. Based on previously reported literature [33–35] that showed a significantly lower activity level of missense mutations in the nonamer-binding region (NBR) that is part of the catalytic core, we can assume that the p.R404W could explain the SCID phenotype observed in PID-8. Here, RAG1 is linked to severe combined immunodeficiency.