Infants with autosomal recessive SCID caused by mutations in recombination activating genes 1&2 (RAG1 &RAG2) [13] that are necessary for the somatic rearrangement of antigen receptor genes on T- and B-lymphocytes [14,15], or in DCLRE1C (Artemis) [16], resemble all other forms of SCID in their infection susceptibility, however their lymphocyte phenotype is charecterized by predominantly circulating NK cells and undetectable B or T lymphocytes (T-B-NK+ SCID) [13]. The gene discussed is RAG2; the disease is severe combined immunodeficiency.