Overview
Omenn syndrome is a severe combined immunodeficiency characterized by a lack of functional T cells due to a somatic mutation in a gene involved in V(D)J recombination, typically combined with a leaky or partially functional B cell compartment. It presents with early-onset infections, organomegaly, and often features of IPEX syndrome due to activation of self-reactive T cells 1.Diagnosis
Key Diagnostic Criteria:
- Presence of reticuloendotheliosis and eosinophilia 1
- Deficiency in lymphocyte ecto-5'-nucleotidase activity 1
Recommended Tests:
- Lymphocyte function assays including ecto-5'-nucleotidase activity measurement 1
- Genetic testing for mutations in recombination-activating genes (RAG1, RAG2) 1Management
First-Line Treatments:
- Hematopoietic stem cell transplantation (HSCT) is the definitive treatment 1
Adjunctive Treatments:
- Immunoglobulin replacement therapy to manage infections 1
- Antimicrobial prophylaxis to prevent opportunistic infections 1Special Populations
Pediatrics: Early diagnosis and prompt HSCT are critical for survival 1Key Recommendations
Measure lymphocyte ecto-5'-nucleotidase activity to aid in distinguishing Omenn syndrome from other immunodeficiencies (Evidence: Moderate) 1
Prioritize hematopoietic stem cell transplantation as the primary treatment strategy (Evidence: Expert opinion) 1
Implement immunoglobulin replacement therapy to support immune function in patients undergoing HSCT or those awaiting transplantation (Evidence: Moderate) 1References
1 Gelfand EW, McCurdy D, Rao CP, Cohen A. Absence of lymphocyte ecto-5'-nucleotidase in infants with reticuloendotheliosis and eosinophilia (Omenn's syndrome). Blood 1984. link