Endothelial proliferation in paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a disorder of stem cells that is associated with venous thrombosis in multiple organ sites. We present a patient with necrotizing pharyngitis and intestinal infarction who has classic laboratory findings for PNH: positive complement-mediated acid and sucrose hemolysis and absence of decay accelerating factor (DAF) in peripheral blood leukocytes. Histopathologic examination of tissue from tonsil and large bowel demonstrated not only venous thrombosis but unusual proliferation of endothelial cells (papillary endothelial hyperplasia). This has not been described previously. We speculate that the endothelial cell in PNH may share in the defective regulation of complement activity. Venous thrombosis could precipitate or be a consequence of these vascular changes.