ARSA and lysosomal storage disease: The most common type of MLD disease is an autosomal recessive inherited lysosomal disorder caused by mutations in the ARSA gene, located on the chromosome 22q13.33, resulting in a deficiency of the enzyme arylsulfatase A. The low activity of arylsulfatase A results in the accumulation of sulfatides in the central and peripheral nervous systems, leading to demyelination (van Rappard et al., 2015).