Myeloablative conditioning for marrow transplantation in myelodysplastic syndromes and paroxysmal nocturnal haemoglobinuria.

Paroxysmal nocturnal haemoglobinuria (PNH) and myelodysplastic syndromes (MDS) are disorders of pluripotent stem cells resulting in haematopoietic insufficiency which can be cured by marrow transplantation. The extent of myeloablative conditioning necessary for elimination of the non-malignant and premalignant clones is not known. We report our results of marrow transplantation with and without myeloablative conditioning in two patients with PNH and seven patients with MDS. Conditioning was not used in a patient with PNH and a monozygotic twin as donor. In this patient the disease remained unchanged. Myeloablative treatment with busulphan (BUS) in addition to immunosuppression with cyclophosphamide (CY) was used for conditioning in a patient with PNH and a 2-year-old boy with chronic myelomonocytic leukaemia (CMML). Fractionated total body irradiation (FTBI) and CY was used in six patients with refractory anaemia with excess of blasts (RAEB) and RAEB in leukaemic transformation (RAEB-T). Haematopoiesis was fully restored in all patients conditioned with myeloablative treatment except for a patient in leukaemic transformation with myelofibrosis and a HLA-DR-incompatible donor. Chimerism was complete in all patients except for the 2-year-old boy conditioned with BUS and CY. Our results and those reviewed in the literature indicate that myeloablative conditioning with either BUS or FTBI is advantageous for marrow transplantation in PNH and MDS.