Ferritin in human liver cells of homozygous beta-thalassaemia: ultrastructural observations.

Homozygous beta-thalassaemia is a disease in which there is a progressive iron overload from infancy to death in early adulthood. Liver biopsies from 10 patients in various stages of this disease were examined by electron microscopy. A number of round or oval lysosomal structures, containing lamellae different from myelin figures, were seen in all patients, including those with minimal iron overload. Ferritin molecules were seen either in relationship with the lamellae forming arrays, or in paracrystalline arrangement, or with no organized form. There were practically no ferritin molecules in sub-cellular compartments other than cell sap and lysosomes. The density of cell sap ferritin was constant beyond infancy, but the number of iron-laden lysosomes increased with age. The stages in the process of iron seclusion, seen even in advanced phases of iron overload, are described. Ferritin is thought to accumulate in lysosomes by a transmembraneous movement, but other explanations are considered.