pediatrics
Metachromatic Leukodystrophy
Introduction
Metachromatic leukodystrophy is a Sphingolipidoses , an inherited disorder of metabolism, caused by arylsulfatase A deficiency. There are several forms, the most severe of which causes progressive paralysis and dementia resulting in death by age 10 years. For more information, see table Some Sphingolipidoses . See also Approach to the Patient With a Suspected Inherited Disorder of Metabolism . In metachromatic leukodystrophy, arylsulfatase A deficiency causes metachromatic lipids to accumulate in the white matter of the central nervous system, peripheral nerves, kidney, spleen, and other visceral organs; accumulation in the nervous system causes central and peripheral demyelination. Numerous mutations exist; patients vary in age at onset and speed of progression. Theinfantile formis characterized by progressive paralysis and dementia usually beginning before age 4 years and resulting in death about 5 years after onset of symptoms. Thejuvenile formmanifests between 4 years and 16 years of age with gait disturbance, intellectual impairment, and findings of peripheral neuropathy. Contrary to the infantile form, deep tendon reflexes are usually brisk. There is also a milderadult form. Diagnosis of metachromatic leukodystrophy is suggested clinically and by findings of decreased nerve conduction velocity; it is confirmed by DNA analysis and/or detecting enzyme deficiency in white blood cells or cultured skin fibroblasts. (Also see Initial testing .) There is currently no effective treatment for metachromatic leukodystrophy in patients with advanced symptoms. Bone marrow or stem cell transplantation may stabilize neurocognitive function in mildly symptomatic forms of the disease. Several other therapeutic options are currently being investigated, primarily in late infantile forms of the disease, including gene therapy, enzyme replacement therapy, substrate reduction therapy, and, potentially, enzyme enhancement therapy. 