Clinical characteristics and molecular analysis of three Chinese children with Omenn syndrome

Omenn syndrome (OS) is a rare autosomal recessive genetic disorder and presents symptoms of severe combined immunodeficiency characterized by erythrodermia, eosinophilia, hepatosplenomegaly, lymphadenopathy, and elevated serum IgE levels. OS has been found to be caused by mutations in RAG1 or RAG2 gene that result in partial V(D)J recombination activity. No study on OS has been reported in Chinese children so far. In this study, the genotype and phenotypes of three infants with OS from three unrelated Chinese families were investigated. All the three children had most of the characteristics of OS except normal serum IgE level. Compound heterozygosity mutations in RAG1 gene (1983 G>A; 2444 C>T and 2219 C>T; 3127 C>G) were identified in two cases, and a homozygous deletion mutation with a premature stop codon was found at residue 2302 of RAG1 gene (2302delT, I729X) in the remaining case, including three novel mutations (2302delT, I729X; 2219 C>T, R699W; and 3127 C>G, Y1001X). Spectratyping analysis of T-cell receptor β-chain variable region (TCRVβ) gene rearrangement was performed in case 1 and case 2. All the 25 TCRVβ subfamilies presented monoclonal or oligoclonal peaks in case 1 and 11 TCRVβ subfamilies were very weak or even absent in case 2. This was the first report about OS in Chinese children. Molecular genetic testing represents an important tool for early confirmed diagnosis and may allow accurate carrier detection and prenatal diagnosis.