Few publications focus on the mysterious, genetically acquired disease paroxysmal nocturnal hemoglobinuria (PNH) and the related "intractable" disorders—aplastic anemia and myelodysplastic syndromes. Now, however, the latest understanding of the clinical and molecular genetic aspects of PNH is summarized here in the proceedings of the International Symposium held in Tokyo in 2001. Major topics reviewed include the molecular mechanisms of the PIG-A gene mutation; complement activation and inhibitors; experimental animal models; pathogenesis; the history of PNH research; the natural history of the disease; the mechanism of PNH clone expansion; the emergence of PNH clones under bone marrow failure syndromes; and treatment of the disease by immunosuppressive agents and stem cell transplantation. This book provides an invaluable summary of current research on the fundamental aspects of PNH pathology, presented by renowned experts in the field.