Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare acquired clonal blood disease caused by a deficiency of phosphatidylinositol glycan class A (PIG‐A) protein, crucial for synthesizing a glycolipid known as glycosylphosphatidylinositol (GPI) anchor that attaches surface proteins to the cell membrane. The gene discussed is PIGA; the disease is paroxysmal nocturnal hemoglobinuria.