Frequency of the arylsulphatase A pseudodeficiency allele in the Spanish population.

Pseudodeficiency in arylsulphatase A (ASA) is a relatively frequent condition in healthy individuals. It produces a reduction in enzyme activity similar to that found in metachromatic leukodystrophy (MLD). Unambiguous discrimination between the two conditions cannot be achieved through conventional enzyme activity assays. A PCR method has been developed which detects the pseudodeficiency (pd) allele using a single pair of primers encompassing the mutation site and hair follicles as the source of DNA. The frequency of this allele in the Spanish population has been evaluated and correlations between different genotypes and ASA activity levels have been established. Ten out of 55 individuals were heterozygous for the ASA pd allele, while two were homozygous. The allele frequency was thus 12.7%.