Metachromatic leukodystrophy
| Metachromatic leukodystrophy | |
|---|---|
 |
|
| Sulfatide | |
| Classification and external resources | |
| Specialty | endocrinology |
| ICD-10 | E75.25 |
| ICD-9-CM | 330.0 |
| OMIM | 250100 |
| DiseasesDB | 8080 |
| MedlinePlus | 001205 |
| eMedicine | ped/2893 |
| MeSH | D007966 |
Metachromatic leukodystrophy (MLD, also called Arylsulfatase A deficiency) 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. Metachromatic leukodystrophy, like most enzyme deficiencies, has an autosomal recessive inheritance pattern.
Like many other genetic disorders that affect lipid metabolism, there are several forms of MLD, which are late infantile, juvenile, and adult.
Palliative care can help with many of the symptoms and usually improves quality of life and longevity.
Carriers have low enzyme levels compared to their family population ("normal" levels vary from family to family) but even low enzyme levels are adequate to process the body's sulfatide.
MLD is directly caused by a deficiency of the enzyme arylsulfatase A (ARSA) and is characterized by enzyme activity in leukocytes that is less than 10% of normal controls. However, assay of the ARSA enzyme activity alone is not sufficient for diagnosis; ARSA pseudodeficiency, which is characterized by enzyme activity that is 5~20% of normal controls does not cause MLD. Without this enzyme, sulfatides build up in many tissues of the body, eventually destroying the myelin sheath of the nervous system. The myelin sheath is a fatty covering that protects nerve fibers. Without it, the nerves in the brain (central nervous system - CNS) and the peripheral nerves (peripheral nervous system - PNS) which control, among other things the muscles related to mobility, cease to function properly.
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