Glycosilphosphatidylinositol-anchored cell surface proteins deficiency in Mexican mestizo patients with aplastic anemia

The peripheral blood cells of ten patients with biopsy-proven aplastic anem ia were studied by means of flow-cytometry in order to assess the expressio n of two phosphatidylinositol-anchored surface proteins: CD55/DAF (decay ac celerating factor) and CD59/MIRL (membrane inhibitor of reactive lysis). An abnormal expression was found in five of these ten patients, whereas the " traditional" tests for paroxysmal nocturnal hemoglobinuria (PNH) were posit ive only on two of these five individuals. Five of the aplastic patients we re treated with anti-thymocyte globulin and cyclosporin-A and three entered a complete remission; of the latter, one had CD55/CD59 deficiencies wherea s two did not. Along the study period one patient with a hemolytic pattern of PNH was identified. It is concluded that CD55 and/or CD59 abnormalities are frequent in Mexican mestizo patients with aplastic anemia, that the apl astic presentation of PNH is more frequent in Mexico than the hemolytic pre sentation, that the flow-cytometric identification of GPI-anchored proteins is more sensitive than the "traditional" PNH tests, and that some patients with PNH-aplasia may respond to intensive immunosuppressive treatment. The flow-cytometric identification of GPI-anchored cell surface proteins shoul d replace the "traditional" tests in the identification of patients with PN H.