The fate of excessβ‐globin chains within erythropoietic cells inα‐thalassaemia 2 trait,α‐thalassaemia 1 trait, haemoglobin H disease and haemoglobin Q‐H disease: an electron microscope study

摘要

Summary.Electron microscope studies have been performed on bone marrow cells from individuals with variousα‐thalassaemia syndromes. Globin chain precipitates were rarely found in the erythropoietic cells of a subject withα‐thalassaemia 2 trait. By contrast, such precipitates were found in 0.6–1.3 of the erythroblast and marrow reticulocyte profiles in two cases ofα‐thalassaemia 1 trait, 2.1–13.7 of profiles in five patients with haemoglobin H (HbH) disease and 6.2 of profiles in one patient with haemoglobin Q‐H (HbQ‐H) disease. In the patient with HbQ‐H disease, but not in the others, the nuclei of some erythroblasts displayed the ‘Swiss cheese’appearance which has been reported in some forms of congenital dyserythropoietic anaemia. It is proposed that inα‐thalassaemia 2 trait, where the degree of excess ofβ‐chains is slight, most of the excess chains are degraded by proteolysis. Inα‐thalassaemia 1 trait, where there is a greater excess ofβ‐chains, the excess chains can undergo either proteolysis or precipitation, but there is little or no tetramerization to form soluble HbH. Finally, in HbH disease, where the degree of excess is considerable, the excessβ‐chains may be subject to proteolys