Mucolipidosis type IV: a mild form with late onset.

A 16-year-old girl is presented with mild clinical manifestations and late onset of mucolipidosis type IV (MLIV). The patient, an Ashkenazi Jew, has had minor motor difficulties and mild psychological disturbances since early childhood. Her vision began deteriorating at 12 years of age, due to bilateral corneal opacities and retinal degeneration. At present she attends a regular high school, although she is slow and scholastic achievements are lower than average. Electron microscopic examination and biochemical studies were typical for MLIV, namely, abnormal ganglioside retention and typical pattern of phospholipids accumulation. This very mild presentation of MLIV suggests a broader spectrum of heterogeneity of this disorder and raises the possibility that MLIV, at least among Ashkenazi Jews, might be more frequent than estimated hitherto, due to undiagnosed mild patients.