CTLA-4 haploinsufficiency with autoimmune sequelae (CHAI) and lipopolysaccharide-responsive and beige-like anchor protein (LRBA) deficiency with autoantibodies, Treg defects, autoimmune infiltration and enteropathy (LATAIE) are human genetic disorders associated with deficient CTLA-4 expression and function. Here, CTLA4 is linked to autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency.