Janus kinase 3 deficiency

Janus kinase 3 deficiency, often written JAK3 deficiency, is a failure of cytokine receptor signalling caused by mutations in the JAK3 gene. JAK3 encodes a tyrosine kinase that is switched on only by cytokines whose receptors share the common gamma chain, including those for interleukins 2, 4, 7, 9, 15 and 21, and it helps regulate the maturation of B cells, T cells and natural killer cells. When the kinase fails, affected people lack T cells and natural killer cells, while their B cells are present at normal levels but work poorly. The result is a form of autosomal severe combined immunodeficiency in which infants suffer repeated and persistent infections, chronic diarrhea, oral thrush, pneumonia and skin rashes, and grow more slowly. Without treatment, those with JAK3-deficient SCID usually live only into early childhood. Allogeneic hematopoietic stem cell transplantation has proved life-saving, and gene therapy is being explored as an alternative. This entry records what the sources state and is not medical advice.