MUCOLIPIDOSIS-IV - MORPHOLOGY AND HISTOCHEMISTRY OF AN AUTOPSY CASE

Mucolipidosis Type IV is a rare, autosomal recessive disorder characte rized by corneal opacification, mental retardation, and delayed motor milestones. Whereas lysosomal storage material has been demonstrated i n biopsied tissues and leukocytes, the complete autopsy pathology, inc luding neuropathology, is unknown. The metabolic defect remains specul ative. We report the general and neuropathologic findings of the only known autopsy. In the central nervous system, neuronal loss in the cer ebral cortex. basal ganglia, deep cerebellar nuclei, and brainstem nuc lei was marked by astrocytosis; the cytoplasm of residual neurons had brown granules. These granules were positive with periodic acid-Schiff , Concanavalia ensiformis, and Sudan black, but not with Luxol-fast bl ue. Ultrastructurally, neurons contained lysosomes laden with osmiophi lic, amorphous and granular material, and few lamellated membrane stru ctures. Hepatocytes, epithelia, endothelia, chondrocytes, and tissue m acrophages also stained positively with Datura stramonium and Ricinus communis-I agglutinins, with renal glomeruli also staining with peanut agglutinin; most non-neural cells contained osmiophilic granules on t oluidine blue-stained, plastic embedded sections, corresponding to lam ellated membrane structures. These findings complement the previously reported ocular morphology and brain and liver biochemistry performed in the same patient, and suggest that the storage material in neurons differs from that in non-neural cells. Furthermore, the underlying def ect is not likely to be a deficiency of a single enzyme (i.e, a lysoso mal hydrolase).