Severe combined immunodeficiency caused by a splicing abnormality of the CD3δ gene

CD3δ deficiency is a recently identified rare form of severe combined immunodeficiency. We analysed the CD3δ gene in a Japanese family with severe combined immunodeficiency. The patients lacked T-cells with normal numbers of B-cells and natural killer cells in peripheral blood. We found a novel homozygous mutation in the splicing acceptor site of intron 2 (IVS2-2A→G) in these patients. Analysis of patients' mononuclear cells revealed the CD3δ splicing abnormality. Chest X-ray films and computed tomography revealed small sized thymuses in these patients. Conclusion:The CD3δ gene should be analysed in patients with severe combined immunodeficiency lacking T-cells with normal B- and natural killer cells irrespective of the thymus size.