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A case of late onset metachromatic leukodystrophy with a clinical picture of paranoid hallucinatory psychosis and severe dyskinesia is described. The problem of diagnostic recognition is discussed. In the case, diagnostic procedures were initiated after atypical clinical course, and established on the basis of MRI and specific biochemical tests.

This is a report of one of the few cases of an adult form of metachromatic leukodystrophy with almost exclusively psychiatric symptoms. This should point out the importance of a careful organic diagnostic assessment in all patients with the first manifestation of a psychiatric disease. In this case an investigation of the patient's family confirmed the heterozygote genetic origin of the disease.

Examining the members of a family the validity of chemical analysis, neurophysiology and neuroimaging for the diagnosis of metachromatic leukodystrophy (MLD) is discussed. As the arylsulfatase A is not decreased in all cases, the neuroimaging (cranial computerized tomography--at a less extend magnetic resonance imaging) gains a particular diagnostic significance. But neither for neuroimaging nor for neurophysiological findings the results are specific. The histological findings have to back up the diagnosis.

A 4 1/2 year old boy without previous neurologic disorders developed chronic hemorrhagic pancreatitis and was shown to have polyposis of the gallbladder. Neurologic symptoms emerged at the age of 5 years. The sonographic pattern of an echogenic gallbladder was suspect of metachromatic leukodystrophy. The definitive diagnosis was made by the findings of very low arylsulfatase A activity in the white blood cells and deposits of sulfatides in the stroma of the polyps of the gallbladder.

Metachromatic leucodystrophies (MLD) comprise a small group of heredodegenerative disorders of the nervous system. Deficiency of sulfatide-sulfatase or arylsulfatase A is the common defect in all forms of MLD leading to lysosomal sulfatide storage in the nervous tissue and in the kidney. On the basis of animal experiments, experiments with cultured fibroblasts of the patients as well as ultrastructural studies in a case of prenatal MLD, the following pathomechanism is proposed: 1. Lysosomal degradation of a large portion newly synthetised sulfatide normally regulating the net synthesis and incorporation of sulfatide into myelin, causes early accumulation of sulfatide in lysosomes of myelinating cells and in neurons in the genetic deficiency of arylsulfatase A. 2. Early accumulation of sulfatide does not lead to disturbance in myelination. Demyelination occurs possibly by storage of a cytotoxic compound, psychosin sulfate, also a substrate for the missing enzyme. Prevention of MLD is possible by prenatal diagnosis of arylsulfatase A deficiency in cultured amniotic cells. Enzyme substitution of the missing arylsulfatase A is possible by exogenous uptake of the enzyme in cultured fibroblasts. Thereby the defect of sulfatide degradation can be corrected. Although principles of enzyme substitution have been demonstrated, the problems of treating patients with MLD with arylsulfatase A infusions have yet to be overcome.