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Combined immunodeficiency due to partial RAG1 deficiency
Combined immunodeficiency due to partial RAG1 deficiency is a form of combined T and B cell immunodeficiency (CID; see this term) characterized by severe and persistent cytomegalovirus (CMV) infection and autoimmune cytopenia.
- CID due to partial RAG1 deficiency
- CID with expansion of gamma delta T cells
- Combined immunodeficiency with expansion of gamma delta T cells
- Prevalence: <1 / 1 000 000
- Inheritance: Autosomal recessive
- Age of onset: Infancy, Neonatal
- ICD-10: D81.8
- OMIM: 609889
- UMLS: C1835931
- MeSH: -
- GARD: -
- MedDRA: -
Prevalence is unknown. To date, 9 cases have been reported.
Patients present before the age of one year with severe disseminated CMV infection, which can manifest with fever and splenomegaly, and recurrent and severe co-infections including sepsis and pneumonitis. Autoimmune cytopenia also occurs and can include autoimmune hemolytic anemia (see these terms) or neutropenia.
SCID due to partial RAG1 deficiency is caused by hypomorphic mutation in the RAG1 gene (11p13). This results in oligoclonal expansion of T cell receptor (TCR) gamma-delta T cells and TCR alpha-beta T cell lymphopenia, although total lymphocyte counts are normal, in combination with CMV infection and autoimmunity.
Diagnosis is based on clinical evaluation, immunological investigation, including lymphocyte subset phenotyping, lymphocyte proliferation to mitogen stimulation, immunoglobulin levels and antibody response to vaccine antigens, and genetic confirmation.
Differential diagnoses include other combined immunodeficiencies.
Prenatal diagnosis can be performed in families where there is a family history and in which the genetic mutation has been identified.
Transmission is autosomal recessive.
Management and treatment
Treatment involves antiviral treatment and management of recurrent infections. Bone marrow transplant has been attempted but may result in graft versus host disease (GVHD; see this term) associated with reactivation of CMV disease. Patients should be treated in centers with experience of transplanting complex primary immunodeficiencies.
The majority of patients reported to date have died within the first few years of life.