Arylsulphatase A and B in juvenile metachromatic leukodystrophy.

A series of five living patients with juvenile metachromatic leukodystrophy (MLD), ten first-degree relatives, and a number of controls were subjected to biochemical investigations including quantitative determination of arylsulphatase A (ASA) and B (ASB) activities in peripheral leukocytes and polyacrylamide disc gel elctrophoresis of arylsulphatases. Five relatives were family members of four previously deceased patients with juvenile MLD. The mean ASA activity of the patients was 1.3 nmol of p-nitrocatechol sulphate hydrolysed in 30 min per mg protein. It was 84 nmol in the relatives, 129 nmol in other neurological patients and 136 nmol in normal controls. The corresponding ASB activity was 38 nmol in the patients, 49 nmol in the relatives, and 99 nmol in normal controls. An extremely low ASB activity, 3.4 nmol, was found in one relative. No ASA band could be visualised in the enzyme electrophoretic patterns of the patients' leukocytes but the bands representing ASB appeared normal. Seven relatives showed ASA bands weaker than normal, and the relative with low ASB activity exhibited very weak ASB band. The low ASB activity in the patients and heterozygotes may be a characteristic feature of the slowly progressive juvenile type MLD diagnosed in the present series.