Paroxysmal nocturnal hemoglobinuria (PNH) is a rare and progressive hematopoietic stem cell disorder in which hematopoietic cells are deficient in glycosylphosphatidylinositol (GPI), which leads to a lack of the complement inhibitor proteins CD55 and CD59 on the surface of blood cells. Here, CD59 is linked to paroxysmal nocturnal hemoglobinuria.