ARSA Variant Associated With Late Infantile Metachromatic Leukodystrophy and Carrier Rate in Individuals of Ashkenazi Jewish Ancestry.

Metachromatic leukodystrophy (MLD) is a rare neurodegenerative lysosomal storage disease resulting from bi-allelic pathogenic variants in the ARSA gene. MLD is distinguished clinically based on the age of onset into late-infantile, juvenile, and adult. The late-infantile type is the most severe phenotype presenting with hypotonia, weakness, gait abnormalities, which progresses to mental and physical decline leading to early death. MLD is considered to be pan-ethnic and no founder variants have previously been described in the Ashkenazi Jewish population. We identified three unrelated individuals of Ashkenazi Jewish descent with homozygosity or compound heterozygosity for the c.178C>T (p.Arg60Trp) variant in the ARSA gene, with a phenotype consistent with late-infantile MLD. The carrier frequency was calculated among 93,293 individuals of Ashkenazi Jewish descent through the Dor Yeshorim screening program and found to have a carrier frequency on 1 in 1554 or 0.06%, which may be representative of a founder variant. Molecular protein modeling showed that the variant affects regional folding. Late-infantile MLD should be considered when the c.178C>T (p.Arg60Trp) variant in the ARSA gene is present in either the homozygous or the compound heterozygous states.