Allogeneic hematopoietic cell transplantation for paroxysmal nocturnal hemoglobinuria

Background: Although allogeneic hematopoietic cell transplantation (HCT) has a potential to cure patients with paroxysmal nocturnal hemoglobinuria (PNH), appropriate indication and conditioning regimen for HCT have not been established. Patients and Methods: Between July 1999 and December 2001, five patients with PNH underwent allogeneic HCT: three for refractory hemolysis and two for aggravating cytopenia. Four patients with hypercellular marrow received Bu-Fludara-ATG (busulfan 4 mg/kg/d for 2 d, fludarabine 30 mg/m2/d for 6 d, and ATG 20 mg/kg/d for 4 d) for conditioning therapy and one patient with hypocellular marrow was conditioned with Cy-ATG (cyclophosphamide 50 mg/kg/d for 4 d and ATG 30 mg/kg/d for 3 d). Three patients received stem cell graft from matched sibling donor and two patients from 1-antigen mismatched unrelated donor. Results: One patient who was conditioned with Bu-Fludara-ATG failed to engraft and died at post-transplant day 62. The other four patients showed three lineage engraftment and normal expression of CD55 and CD59 antigens by flow cytometric analysis. They are alive with stable engraftment and full donor chimerism between post-transplant day 510 and 1116. Acute graft vs. host disease (GVHD) of grade II or more occurred in two patients and extensive chronic GVHD in four. Conclusion: HCT using related or unrelated donor could eradicate PNH clones and may cure patients with the disease. Further studies are needed to establish the role of allogeneic HCT, especially with reduced intensity conditioning therapy, in the treatment of PNH.