Abstract
Metachromatic leukodystrophy (MLD) is a rare inherited neurodegenerative disease associated with a defect in the catabolism of sulphatide (galactocerebroside-sulphate) which accumulates in the nervous system. MLD can be diagnosed biochemically by demonstrating deficiency in the activity of the enzyme arylsulphatase A (ASA) and an excess of sulphatide in urine and tissues.
Cinically adult MLD may present as a schizophrenic-like psychosis, which typically develops years before the onset of neurologial signs which are not inevitable. Urinary ASA was investigated in 99 chronic hospitalized psychiatric patients (including 77 schizophrenics). Thirteen showed reduced ASA activity. Of the nine who were available for further study, only one evinced reduced ASA activity in other tissues (for example, leukocytes and cultured fibroblasts). However, there was no evidence of sulphatidurea with impaired sulphatide hydrolysis in his intact cultured fibroblasts. Therefore, he tested negative for MLD. This biochemical profile is known as pseudosulphatase deficiency. The possible relationship of pseudosulphatase deficiency to schizophrenic-like conditions is discussed.