Autoimmune lymphoproliferative disorders, including autoimmune lymphoproliferative syndrome (ALPS) and Dianzani autoimmune lymphoproliferative disease (DALD), are inherited defects of the Fas apoptotic pathway characterized by lymphoid accumulation and autoimmune manifestations. We report the molecular, clinical, immunologic features and the long-term progress of 31 patients. Four carried Fas gene mutations and one also displayed a caspase 10 polymorphism that probably contributed to the phenotype. Seven patients developed antibody deficiency and their clinical pictures overlapped those of subjects with common variable immunodeficiency (CVID). We postulate the existence of a disorder that involves the Fas pathway and displays the characteristics of both autoimmune lymphoproliferative disease and CVID.