Non-progressive psychomotor retardation in a child with severe deficiency of arylsulphatase A activity.

Severe deficiency of arylsulphatase A (ARSA) activity was detected in a boy with delayed psychomotor development, coarse face and liver enlargement when he was aged 2. The case does not fit into the description of the Metachromatic leukodystrophy (MLD) proposed by Hagberg (1963) mainly because he did not deteriorate. Twelve years of follow up did not show any signs of decerebration or further intellectual decline; only speech was, and still is, absent. The reduced ARSA activity in leukocytes and fibroblasts of the father of the propositus suggests that he is heterozygote and that the ARSA deficiency of the propositus is inherited. The ARSA activity of the mother overlaps with the lowest control. The assumption that the mother is a carrier of different mutations could explain the discrepancy between the clinical and biochemical findings of the patient. This is a further family in which mutations other than the typical one can be postulated to explain variable clinical or biochemical pictures of MLD.