Prevalence of Arylsulfatase A Pseudodeficiency Allele in Metachromatic Leukodystrophy Patients from Poland

Arylsulfatase A (ASA) pseudodeficiency (PD) allele was searched for in 22 patients originating from Poland and suffering from different types of metachromatic leukodystrophy (MLD). Four of them carried the PD allele in a heterozygous state. The prevalence of the PD allele among investigated MLD patients was revealed to be 9%, while the frequency of the PD allele in healthy controls was estimated at 6–7%. One of the examined MLD patients was additionally a carrier of an isolated mutation leading to the loss of the N-glycosylation site. The question arises whether and how MLD mutations create a convenient milieu for PD mutations to occur (or inversely).