Omenn Syndrome
Pronunciation: OH-men SIN-drohm
A rare, severe combined immunodeficiency variant characterised by erythroderma, hepatosplenomegaly, eosinophilia, and elevated IgE caused by hypomorphic mutations in RAG1 or RAG2 genes that permit oligoclonal T-cell expansion.
Full Definition
Omenn syndrome is a leaky form of severe combined immunodeficiency in which partially functional RAG1 or RAG2 mutations allow the maturation of a restricted repertoire of autoreactive T cells. These oligoclonal T cells infiltrate skin, gut, and liver, producing cytokines that drive the hallmark features of generalised erythroderma, protracted diarrhoea, failure to thrive, hypereosinophilia, and markedly elevated serum IgE despite absent B cells. The condition can be mistaken for graft-versus-host disease or Netherton syndrome on initial presentation, making accurate editorial rendering of diagnostic criteria particularly important. Haematopoietic stem cell transplantation is curative but must be undertaken urgently. 'Omenn' is a proper noun and must always be capitalised; the possessive form ('Omenn's syndrome') is now discouraged in favour of the eponymous non-possessive form.
Usage
Usage note: Use non-possessive form: 'Omenn syndrome', not 'Omenn's syndrome'. Always capitalise as an eponym. Distinguish from graft-versus-host disease, which shares dermatologic features.
In Context
- "Omenn syndrome was confirmed following identification of compound heterozygous RAG1 mutations and the characteristic triad of erythroderma, eosinophilia, and elevated IgE." — Paediatric immunology case report
- "The manuscript initially used 'Omenn's syndrome'; the editor amended this to the non-possessive form in accordance with current convention." — Journal style guide annotation