Hepatic ultrastructure in fucosidosis

The hepatic wedge biopsy of a 3 1/2-year-old boy with fucosidosis was studied by electron microscopy. The cytoplasm of liver parenchymal cells is filled with various forms of membrane-invested storage elements measuring up to 3 μm in diameter. In these storage elements large central deposits of reticulogranular material are surrounded by a narrow peripheral ring of electron-dense material. Others contain numerous lamellar structures with parallel and/or concentric orientation, opaque globules and vesicular structures. Typical peribiliary dense bodies (lysosomes) are generally absent. The storage elements appear to be produced by deposition of storage material in lysosomes. The absence of the lysosomal enzyme α-L-fucosidase is in favor of this concept. Kupffer cells, epithelial cells of the bile canalicular system, vascular endothelial cells of portal tracts and histiocytes are rich in storage elements which are also found in the majority of fibrocytes and fibroblasts. They are uncommon in pericytes and cannot be demonstrated in smooth muscle and fat-storing cells. Ultrastructural features and cellular distribution of storage elements are compared with previous descriptions of related storage disorders.