Lack of either ASA, GALC, or ASAH1 results in a fatal lysosomal storage disease designated as metachromatic leukodystrophy (MLD; OMIM 250100), globoid cell leukodystrophy (Krabbe disease; OMIM 245200), and Farber disease (OMIM 228000), respectively (2). Here, ASAH1 is linked to metachromatic leukodystrophy.