Omenn Syndrome, also known as histiocytic medullary reticulosis, is related to severe combined immunodeficiency, autosomal recessive, t cell-negative, b cell-positive, nk cell-negative and hypereosinophilic syndrome, and has symptoms including diarrhea An important gene associated with Omenn Syndrome is RAG2 (Recombination Activating 2), and among its related pathways/superpathways are Innate Immune System and MIF Mediated Glucocorticoid Regulation. The drugs Busulfan and Fludarabine have been mentioned in the context of this disorder. Affiliated tissues include t cells and b cells, and related phenotypes are failure to thrive and hepatomegaly