Recently, an inherited syndrome characterized by nonmalignant lymphoproliferation with autoimmune manifestations, caused by mutations of the Fas (CD95) receptor gene has been described. Because of disease severity, i.e. unremitting lymphoproliferation in a child with complete Fas deficiency, a haploidentical bone marrow transplantation (BMT) was performed despite the known resistance of Fas-deficient lpr mice to bone marrow transplantation. Marrow graft was rejected early; however, a second attempt using bone marrow from the mother led to engraftment and to control of lymphoproliferation and of autoimmune thrombocytopenia up to the last follow-up at 24 months after BMT. This single case shows that resistance to bone marrow engraftment caused by survival of Fas-deficient cells can be overcome.