Metachromatic leukodystrophy (MLD), is an autosomal recessive disorder of lipid metabolism characterized by the deficient activity of the lysosomal enzyme arylsulfatase A (ASA), resulting in deficient degradation of galactosylceramide-3-O-sulfate (sulfatide) and galactosylsphingosine-3-O-sulfate (lysosulfatide) (Gieselmann, 2008). The gene discussed is ARSA; the disease is metachromatic leukodystrophy.