A new mucolipidosis with psychomotor retardation, corneal clouding, and retinal degeneration

A 23-year-old man had slow psychomotor development at 6 months of age and developed intermittent corneal clouding at about 18 months. He developed a truncal ataxia and hypotonia of the limbs combined with spasticity and active deep reflexes that did not progress. His skeleton and facies were normal. Between 1 and 13 years of age, he developed severe optic atrophy, absence of retinal blood vessels, and an extinguished electroretinogram. Biochemical analysis of cultured fibroblasts indicated no lysosomal hydrolase deficiency; cellular metachromasia was absent and there was no mucopolysaccharidoses. Ultrastructural studies indicated single-membrane-limited vacuoles containing lamellated membranes and a polymorphous substance in tissue-cultured cells and conjunctiva.