DEFICIENCY OF GLYCOSYL PHOSPHATIDYLINOSITOL-ANCHORED PROTEINS IN POLYMORPHONUCLEAR LEUKOCYTES FROM PATIENTS WITH PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA WITH LOW-GRADE HEMOLYSIS

Paroxysmal nocturnal hemoglobinuria (PNH) is a disorder characterized by the deficiency of glycosyl phosphatidylinositol (GPI)-anchored prot eins in blood cell membranes. We experienced a patient with PNH whose grade of hemolysis was reduced during the course of the disease. An an alysis of the expression of GPI-anchored proteins on blood cells revea led typical PNH defects in polymorphonuclear leukocytes (PMN), but not in red blood cells (RBC). Accordingly, we investigated the expression of CD59 on RBC and of CD59 and CD16 on PMN in PNH patients, using imm unofluorocytometry. We examined the cells of 8 PNH patients with diffe rent grades of hemolysis. PNH-affected PMN deficient in CD16 and CD59 were clearly demonstrated in every patient, including those with low-g rade hemolysis. We conclude that demonstration of PNH-affected PMN def icient in GPI-anchored proteins has diagnostic values even in PNH pati ents with low-grade hemolysis.