Zap-70 (zeta-chain-associated protein 70 kD) deficiency is an autosomal recessive form of severe combined immune deficiency (SCID) that is characterized by lack of CD8+ T cells and normal presence of circulating CD4+ T cells. The disease is extremely rare, with only 12 patients from 8 unrelated families reported so far. Nearly all patients with Zap-70 defects presented with typical clinical features of SCID in early life: severe pulmonary infection often sustained by opportunistic pathogens (Pneumocystis carinii), chronic diarrhoea, failure to thrive, and persistent candidiasis. Zap-70 deficiency is ultimately fatal unless patients undergo bone marrow transplantation (BMT). In the future, gene therapy could appear to be an alternative form of treatment. Most of the ZAP-70 gene defects identified in humans prevent protein expression and are concentrated in a region that is critical for stability and enzymatic activity. Mutations include insertions, deletions, and substitutions of a single nucleotide. Antenatal diagnosis by analysis of chorionic villi DNA can be carried out.
Last update: January 2005