Ultrastructural Studies in β‐Thalassaemia Major

S ummary . The peripheral red blood cells of 11 patients with β‐thalassaemia major were studied by electronmicroscopy, and a wide spectrum of intracellular changes was observed. Findings were striking in the six splenectomized individuals and most prominent in reticulocytes and late normoblasts. There was marked accumulation of iron in different forms, either as free particles or as aggregates of ferritin and haemosiderin within membrane‐bound particles or mitochondria. Glycogen accumulation was often found in normoblasts. Cells were grossly distorted and deformed, showing indentations and infolding of the plasma membrane with marked vacuole formation. The most striking finding was the presence of Heinz bodies in various stages of development. These were unlike those encountered in phenylhydrazine induced haemolytic anaemia; no large marginated Heinz bodies were found attached to the cell membrane. The implications of this finding in relation to the present concept of sequestration of Heinz bodies in the spleen are discussed. Another prominent feature was the presence of many bizarre membrane forms and myclin figures which may represent attempts at autodigestion of excess intracellular inclusions, particularly in the absence of the spleen. The wide spectrum of ultrastructural changes found may be an expression of multiple intracellular defects involving the biosynthesis of globin, haem, glycoprotein, and membranes in β‐thalassaemia.