According to the results of the present studies, PIG-A gene mutation is widely considered as one of the pathogenesis of PNH, but there are at least 20 genes that are involved in GPI biosynthesis in addition to PIG-A, and additional genetic changes occurring in PIG-A-mutant HSCs could give these HSC clones a benign growth advantage (2). The gene discussed is PIGA; the disease is paroxysmal nocturnal hemoglobinuria.