Omenn syndrome--review of several phenotypes of Omenn syndrome and RAG1/RAG2 mutations in Japan.

[omenn syndrome]

Omenn syndrome (OS ) is a form of severe combined immunodeficiency (SCID ) characterized by erythrodermia , hepatosplenomegaly , lymphadenopathy , and alopecia . In patients with OS , B cells are mostly absent , T -cell counts are normal to elevated , and T cells are frequently activated and express a restricted T -cell receptor (TCR ) repertoire . Thus far , inherited hypomorphic mutations of the recombination activating genes either 1 or 2 (RAG 1 /2 ) have been detected in most OS patients . We have recently experienced a rare case of OS showing the revertant mosaicism due to multiple second -site mutations leading to typical OS clinical features with RAG 1 -deficient SCID . In this review , we will focus on the variation of several phenotypes of OS .