Late-onset metachromatic leukodystrophy: diagnostic problems elucidated by a case report.

A 20-year-old female had psychiatric symptoms of organic brain disease for five years but without clinical or neurophysiological signs of polyneuropathy. Late-onset metachromatic leukodystrophy was confirmed by finding severely reduced arylsulfatase A activity in her urine and leukocytes, marked excretion of sulfatides in the urine and the presence of lysosomal residual bodies in a sural nerve biopsy. This case report emphasizes the need to screen patients with early onset dementia of unknown origin or atypical hebephrenia, who are often confined to mental institutions early in the course of their disease.