The liver in thalassaemia major: ultrastructural observations

During a study of pathogenetic mechanisms in the hepatic cirrhosis of thalassaemia major, 16 liver biopsies were examined by electron microscopy. Previous ultrastructural studies of liver cells during iron overload have shown electron-dense iron as lysosomal haemosiderin, and as lysosomal and cell-sap ferritin. In this study, all biopsies, regardless of the patient's age, showed ferritin molecules within lysosomes in a specific pattern in relationship with regularly arranged lamellae. This membrane-associated lysosomal ferritin is considered to be a stage in the segregation of iron seen in iron overload. The dimensions and electron density of individual ferritin molecules indicate differences between cell sap and lysosomal ferritin. Intracellular ferritin transport and iron-seclusion mechanisms are reconsidered in view of these findings. The liver biopsies of thalassaemic infants also provide information about the causal relationship between iron overload and collagen deposition. Since the collagen deposition precedes any morphological evidence of cellular injury (other than the increased iron content), the primary cirrhotogenic factor in thalassaemia is apparently not cell necrosis but possibly excessive collagen deposition induced by iron.