omenn syndrome omenn syndrome omenn syndrome is an autosomal recessive severe combined immunodeficiency. it is associated with hypomorphic missense mutations in immunologically relevant genes of t-cells (and b-cells) such as recombination activating genes (rag1 and rag2), interleukin-7 receptor-α (il7rα), dclre1c-artemis, rmrp-chh, dna-ligase iv, common gamma chain, whn-foxn1, zap-70 and complete digeorge syndrome. it is fatal without treatment. omenn syndromeomenn syndrome has an autosomal recessive pattern of inheritance.specialtyhematology symptoms and signs a 5-month-old female infant with omenn syndrome; she has red, scaly skin all over her body. the symptoms are very similar to graft-versus-host disease (gvhd). this is because the patients have some t cells with limited levels of recombination with the mutant rag genes. these t cells are abnormal and have a very specific affinity for self antigens found in the thymus and in the periphery. therefore, these t cells are auto-reactive and cause the gvhd phenotype. a characteristic symptom is chronic inflammation of the skin, which appears as a red rash (early onset erythroderma). other symptoms include eosinophilia, failure to thrive, swollen lymph nodes, swollen spleen, diarrhea, enlarged liver, low immunoglobulin levels (except immunoglobulin e, which is elevated), low t cell levels, and no b cells. genetics omenn syndrome is caused by a partial loss of rag gene function and leads to symptoms similar to severe combined immunodeficiency syndrome, including opportunistic infections. the rag genes are essential for gene recombination in the t-cell receptor and b-cell receptor, and loss of this ability means that the immune system has difficulty recognizing specific pathogens. omenn syndrome is characterised by the loss of t-cell function, leading to engraftment of maternal lymphocytes in the foetus and the co-existence of clonally expanded autologous and transplacental-acquired maternal lymphocytes. omenn syndrome can occasionally be caused in other recombination genes, including il-7rα and rmrp. diagnosis in order to diagnose a patient specifically with omenn syndrome, an autosomal recessive form of scid, a physician can order a genetic testing panel to look for 22q11 microdeletions or mutations of the rag1/rag2 genes. treatment the only treatment for omenn syndrome is chemotherapy followed by a bone marrow transplantation. without treatment, it is rapidly fatal in infancy.