Paroxysmal nocturnal hemoglobinuria following alemtuzumab immunosuppressive therapy for myelodysplastic syndrome and complicated by recurrent life-threatening thrombosis despite anticoagulation: successful intervention with eculizumab and fondaparinux.

The pathogenesis of paroxysmal nocturnal hemoglobinuria (PNH) is not fully understood. We report a patient with myelodysplastic syndrome who developed symptomatic PNH following treatment with alemtuzumab. A small PNH clone, identified prior to alemtuzumab, expanded resulting in hemolytic anemia and recurrent CNS thromboses despite anticoagulation. Remission was achieved with eculizumab and fondaparinux therapy. Alemtuzumab has been associated with the development of glycosylphosphotidylinositol negative cells, but its clinical significance has been unclear. Our case emphasizes its potential clinical importance. Future studies are necessary to expand our understanding of this rare disease entity and improve its management.