PIGA and paroxysmal nocturnal hemoglobinuria: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired, nonmalignant, clonal hematopoietic stem cell disorder characterized by somatic mutations in PIG-A gene accompanied by additional secondary events leading to defective biosynthesis of cell-surface membrane glycophosphatidylinositol (GPI) [1].