Erythropoiesis in paroxysmal nocturnal hemoglobinuria.

Ten patients with paroxysmal nocturnal hemoglobinuria were studied. The diagnosis was made on the basis of hemolytic anemia, a positive Ham test and hemosiderinuria. Six patients had primary paroxysmal nocturnal hemoglobinuria evolved from aplastic anemia. These four patients also had a milder form of the disease, Over long periods of the follow-up, large variations of hemoglobin values and red blood cell counts were observed. Both absolute and percent reticulocyte counts were increased. Erythroblast counts in the bone marrow were 3-5 times higher than normal. Reticulocyte counts in the bone marrow were 3-5 times higher than normal. Reticulocyte counts showed wide variations but substantially smaller than those in autoimmune hemolytic anemias. Serum iron was either normal or increased, while the bone marrow iron store was high or low. However, the finding of urinary hemosiderin in all cases spoke against depletion of iron stores. The red blood cell life span was moderately shortened. Kinetic studies with 59Fe showed a high red blood cell iron incorporation, while the curves frequently had irregular shapes (broken curve) or an early, abrupt fall. Studies of late erythroid progenitors (CFU-E) indicated that this compartment was preserved. Even after long observation periods was no stem cell pool depletion due to an increased red blood cell demand observed.