Mucolipidosis IV: ultrastructural diagnosis of a recently defined genetic disorder.

In nine cases of a new genetic disorder mucolipidosis IV clinical findings included early or congenital corneal cloudiness and mild to severe psychomotor retardation in all patients. The diagnosis can be established by electron microscopy of the conjunctiva, which along with several other tissues shows typical ultrastructural changes. All of the known patients described were descendants of parents of Jewish-Ashkenazi origin, and it seems that mucolipidosis IV is another "Jewish" genetic disease. Prenatal diagnosis can be made by finding the typical ultrastructural changes in cells of the amniotic fluid. Biochemical abnormalities are inconspicuous, but there is evidence that the storage materials are gangliosides and hyaluronic acid.