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Chronic, non-malignant hypersplenism with lymphadenopathy, hypergammaglobulinaemia, and autoimmunity was first reported in children in 1967. The condition, now known as autoimmune lymphoproliferative syndrome (ALPS), is further characterised by an abundance of double-negative T cells (lymphocytes with α/β T cell receptors but without CD4 or CD8 surface determinants), and defective lymphocyte apoptosis. Most patients (about three quarters) have heterozygous, germ-line mutations in the Fas gene (TNFRSF6) that controls programmed cell death (apoptosis). These patients are said to have ALPS type I. A few have defects in the genes for caspase 8 and caspase 10—proteins also associated with the process of apoptosis (ALPS type II). In about a quarter of cases, however, no gene defect has been demonstrated (ALPS type III). Now six children with ALPS type III have been examined (
, see also perspective article, ibid: 1388–90) and all six had Fas mutations in their double-negative T cells. In two of the children cells from skin and bucal mucosa were examined and they did not contain the mutation. It is therefore suggested that ALPS type III is associated with somatic Fas mutations in haemopoietic cells and these cases should be reclassified as mosaic ALPS type I or ALPS type Im. …