Dyserythropoiesis associated with a Fas-deficient condition in childhood

Defective lymphocyte apoptosis caused by mutations of the Fas gene can resu lt in an autoimmune lymphoproliferative syndrome (ALPS) in humans. We repor t two cases of dyserythropoiesis associated with a Fas-deficient condition in childhood. In both cases, dyserythropoiesis predominated on the more mat ure erythroblasts, and was associated with a lymphoproliferative syndrome a s well as with haemolytic anaemia, hypergammaglobulinaemia and the expansio n of an unusual population of CD4(-)CD8(-) T cells that express the alpha/b eta T-cell receptor. The regression of dyserythropoiesis under steroid ther apy suggested that it resulted from an autoimmune mechanism, itself seconda ry to the lymphocyte Pas apoptosis deficiency. Fas-defective apoptosis may be a new aetiology for childhood dyserythropoiesis.