CD59 and paroxysmal nocturnal hemoglobinuria: PNH is a clonal disorder of hematopoietic progenitor cells caused by an acquired mutation of the X-linked phosphatidylinositol glycans class A gene.[9] The absence of glycosylphosphatidylinositol anchored complement regulatory proteins CD55 and CD59 from the membrane of circulatory cells is responsible for activation of the complement system on the surface of the red cell membrane.