Intrauterine diagnosis of mucolipidosis IV by electron microscopy

A recently recognized metabolic storage disease, mucolipidosis IV (ML IV), was characterized clinically by corneal opacity in infancy, full facial features and psychomotor retardation. Diagnosis was confirmed by the characteristic storage bodies observed upon electron microscopy (EM) of various biopsied tissues. In a family with an affected daughter, prenatal diagnosis was made in 2 subsequent pregnancies. In both of these, EM examination of the amniotic fluid cell cultures revealed the presence of storage bodies identical to those observed in the conjunctival biopsy and cultured skin fibroblasts of the affected daughter. In the first amniocentesis, performed during the 19th wk of gestation, almost all cultured amniotic fluid cells showed abnormal storage material. The diagnosis in the abortus was confirmed in cells obtained from the culture of the amnion. In the second amniocentesis, performed during the 12th wk of gestation, only 40% of the cultured amniotic fluid cells showed the abnormal storage material. Amniotic fluid cells obtained at the time of pregnancy interruption (17th wk) showed abnormal storage material in most cultured cells. Direct EM examination of uncultured fetal tissues showed characteristic abnormal storage material in nervous and epithelially derived tissues. This case demonstrates that the percentage of cultured amniotic fluid cells which show inclusions may depend on the gestational age of the fetus. It also emphasizes the use of EM investigation in the prenatal diagnosis of those metabolic storage diseases in which the biochemical defect is still undefined.