Mutations in the RAG1 or RAG2 genes may lead to a failure of V(D)J recombination of Ig and TCR genes and are the prominent causes for severe combined immunodeficiency (SCID), such as Omenn syndrome, a form of primary immunodeficiency characterized by abnormal development of functional T cells and B cells [3]. This evidence concerns the gene RAG1 and severe combined immunodeficiency.