Abnormal low and high density lipoproteins in homozygous beta-thalassaemia.

The levels, structure and composition of plasma lipoproteins were determined in 67 patients with homozygous beta-thalassaemia and compared to healthy or heterozygous members of the same families and to patients with either sickle cell or iron deficiency anaemia. Plasma total and LDL and HDL cholesterol levels were low in patients with homozygous beta-thalassaemia and with sickle cell anaemia. Plasma triglycerides did not differ between subjects. The low plasma and lipoprotein cholesterol was independent of age, transfusion requirements and splenectomy. Abnormal structure and composition of lipoproteins was found in homozygous beta-thalassaemia. The LDL was of higher density and was triglyceride-rich and cholesterol ester-poor. HDL separated to three populations. HDL2 was prominent (in spite of low plasma HDL cholesterol). HDL3 was of normal density and an intermediate HDL population, not found in normal subjects, was identified and designated HDL2-3. All three HDL populations were enriched with triglycerides and poor in cholesterol ester content. The modified LDL and HDL particles may then be possibly cleared rapidly from the plasma by activated monocytes and macrophages.