Prenatal diagnosis of mucolipidosis II--electron microscopy and biochemical evaluation.

Prenatal diagnosis of mucolipidosis type II (I-cell disease) can be performed quickly and reliably by electron microscopy of chorionic villus tissue. This study reports the results of studies in three prenatal assessments (two families) where the pregnancy was at one in four risk of the disorder. In all three cases, electron microscopy showed marked vacuolation in chorionic villus cells, consistent with the fetus being affected by the disorder. Further studies in cultured chorionic villus cells showed a marked deficiency of a number of lysosomal enzymes. All pregnancies were terminated. Follow-up studies in fetal tissue (where available) confirmed the prenatal diagnosis as correct.