Metachromatic leukodystrophy (MLD) is a lysosomal storage disease which is commonly listed in the family of leukodystrophies as well as among the sphingolipidoses as it affects the metabolism of sphingolipids. Leukodystrophies affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibers throughout the central and peripheral nervous systems. MLD involves cerebroside sulfate accumulation.[1][2] Metachromatic leukodystrophy, like most enzyme deficiencies, has an autosomal recessive inheritance pattern.[2]

Reference
Wiki: Fatal infantile leukodystrophy