There have been three cases of SCID (0, 0 and 4 TREC copies/μL, respectively) with confirmed diagnosis: in case 1, we could not find causal mutations; in case 2 a RAG2 deficiency was found; a PNP deficiency was found in case 3; establishing an incidence of SCID in Catalonia of one in 74,187 newborns. Here, RAG2 is linked to hyperinsulinemic hypoglycemia, familial, 4.