Mucolipidosis IV: ocular, systemic, and ultrastructural findings.

The ocular and systemic findings in four children with mucolipidosis IV (ML IV), a new variant of mucolipidosis, are described. Corneal clouding from birth or early infancy is a prominent feature in all of the patients and in two of them, this was the presenting symptom. Psychomotor retardation usually does not become apparent until the end of the first year of life. Conjunctival biopsies revealed two types of abnormal inclusion bodies: (1) single-membrane-limited cytoplasmic vacuoles containing both fibrillogranular material and membranous lamellae, and (2) lamellar and concentric bodies similar to those found in Tay-Sachs disease. The abnormal cytoplasmic organelles were present in both the stromal fibroblasts and the epithelial cells. The electroretrinogram performed in one patient was subnormal.