Conjunctival biopsies of six patients with mucolipidosis III (pseudo-Hurler polydystrophy) were studied by light and electron microscopy. Pathologic changes were consistently evident only at the ultrastructural level and involved fibrillogranular material and few lamellar lipid inclusions within lysosomes of fibroblasts, capillary endothelial cells and occasional Schwann cells. The moderate and variable storage evident in these patients' tissues may be consistent with the concept of genetic heterogeneity in multiple lysosomal hydrolase deficiencies and with the hypothesis that mucolipidosis III represents the mild phenotype of I-cell disease.SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe