Dyserythropoiesis in homozygous haemoglobin C disease

Electron microscope studies of the bone marrow of three patients with homozygous haemoglobin C (HbC) disease have shown marked ultrastructural abnormalities in several of the polychromatic erythroblasts and marrow reticulocytes and the presence of phagocytosed erythroblasts within the macrophages. Such abnormalities were not found in the bone marrow of three patients with sickle cell anaemia indicating that the abnormalities represented a feature of HbC disease rather than a disturbance secondary to peripheral haemolysis. The characteristic ultrastructural finding in the polychromatic erythroblasts in HbC disease was the presence of grossly-disorganized nuclei showing multiple intranuclear clefts, the loss of parts of the nuclear membrane, oozing of nuclear material into the cytoplasm and an alteration of the structure and stainability of the nuclear chromatin. It is proposed that both the dyserythropoiesis and ineffective erythropoiesis in HbC disease may have resulted from the formation in vivo of very small aggregates of HbC within erythropoietic cells.