paroxysmal nocturnal hemoglobinuria (PNH), an acquired hemolytic anemia caused by a clonal stem cell mutation that results in an absence of glycosylphosphatidylinositol-anchored proteins, including decay-accelerating factor (DAF) and CD55. Red cells lacking DAF and CD55 have an increased susceptibility to complement activation and lysis, resulting in intravascular hemolysis and hemoglobinuria, especially during sleep.
