Monogenic defects in lymphocyte apoptosis

PURPOSE OF REVIEWThe recognition that apoptosis – programmed cell death – is an important mechanism in immune homeostasis has led to the identification of human disorders associated with defects in the critical control mechanism. RECENT FINDINGSPatients have been identified with defects affecting the extrinsic apoptotic pathway mediated by the protein receptor FAS which results in the autoimmune lymphoproliferative syndrome and more recently in defects affecting the intrinsic apoptotic pathway mediated by RAS proteins resulting in the RAS-associated autoimmune leukoproliferative disorder. This review summarizes the immunopathogenesis, clinical features and diagnostic approaches to these human disorders. SUMMARYApoptotic pathways are critical in the maintenance of leukocyte homeostasis, and genetic defects impacting these can result in clinical disease manifested as expansion of selected leukocyte populations, autoimmunity, increased risk for malignancy and in some situations defects in host defense.