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Metachromatic leukodystrophy (MLD, also called Arylsulfatase A deficiency) is the most common form of a family of genetic diseases known as the leukodystrophies, diseases which affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibres throughout the central and peripherial nervous systems .
MLD is directly caused by a deficiency of the enzyme arylsulfatase A. Without this enzyme, sulfatides build up in many tissues of the body, eventually destroying the myelin of the nervous system.
Symptoms and forms
Like many other genetic disorders that affect lipid metabolism, there are several forms of MLD, which are late infantile, juvenile, and adult.
In the late infantile form, which is the most common form MLD, affected children being having difficulty walking after the first year of life. Symptoms include muscle wasting and weakness, muscle rigidity, developmental delays, progressive loss of vision leading to blindness, convulsions, impaired swallowing, paralysis, and dementia. Children may become comatose. Untreated, most children with this form of MLD die by age 5, often much sooner.
Children with the juvenile form of MLD (onset between 3-10 years of age) usually begin with impaired school performance, mental deterioration, and dementia and then develop symptoms similar to the late infantile form but with slower progression. Age of death is variable, but normally within 10 to 15 years of symptom onset.
The adult form commonly begins after age 16 as a psychiatric disorder or progressive dementia. Adult-onset MLD progresses more slowly than the late infantile and juvenile forms, with a protracted course of a decade or more.
In rare cases the body can compensate for the deficiency and the person will exhibit no symptoms.
There is no cure for MLD, nor a standard form of treatment. Children with advanced juvenile or adult onset, and late infantile patients displaying symptoms have treatment limited to pain and symptom management. Presymptomatic late infantile MLD patients, as well as those with juvenile or adult MLD that are either presymptomatic or displaying mild to moderate symptoms, have the option of bone marrow transplantation, which may slow down the progression of the disease, or stop its progression.
Treatment options for the future that are currently being investigated include gene therapy and enzyme replacement therapy.
- The Myelin Project
- The Stennis Foundation
- Large portions of this article are courtesy of the public domain text available at the National Institute of Neurological Disorders and Stroke 
- Further information regarding MLD, treatments, genetics, and current research projects, can be found at: The Stennis Foundationand The MLD Foundation
- eMedicine article about MLD by Theodore Moore, MD.
Metabolic pathology / Inborn error of metabolism (E70-90, 270-279)
Aromatic (Phenylketonuria, Alkaptonuria, Ochronosis, Tyrosinemia, Albinism, Histidinemia) - Organic acidemias (Maple syrup urine disease, Propionic acidemia, Methylmalonic acidemia, Isovaleric acidemia, 3-Methylcrotonyl-CoA carboxylase deficiency) - Transport (Cystinuria, Cystinosis, Hartnup disease, Fanconi syndrome, Oculocerebrorenal syndrome, Lysinuric protein intolerance) - Sulfur (Homocystinuria, Cystathioninuria, Hawkinsinuria) - Urea cycle disorder (N-Acetylglutamate synthase deficiency, Carbamoyl phosphate synthetase I deficiency, Ornithine transcarbamylase deficiency, Citrullinemia, Argininosuccinic aciduria, Argininemia, Hyperammonemia) - Glutaric acidemia type 1 - Hyperprolinemia - Sarcosinemia - Other Trimethylaminuria - Tetrahydrobiopterin deficiency - Beta-ketothiolase deficiency
Lactose intolerance - Glycogen storage disease (type I, type II, type III, type IV, type V, type VI, type VII) - fructose metabolism (Fructose intolerance, Fructose bisphosphatase deficiency, Essential fructosuria) - galactose metabolism (Galactosemia, Galactose-1-phosphate uridylyltransferase galactosemia, Galactokinase deficiency) - other intestinal carbohydrate absorption (Glucose-galactose malabsorption, Sucrose intolerance) - pyruvate metabolism and gluconeogenesis (PCD, PDHA) -
Pentosuria - Renal glycosuria
Sphingolipidoses/Gangliosidoses: GM2 gangliosidoses (AB variant, Sandhoff disease, Tay-Sachs disease) - GM1 gangliosidoses - Mucolipidosis type IV - Gaucher's disease - Niemann-Pick disease - Farber disease - Fabry's disease - Metachromatic leukodystrophy - Krabbe disease
|Fatty acid metabolism||
Lipoprotein/lipidemias: Hyperlipidemia - Hypercholesterolemia - Familial hypercholesterolemia - Xanthoma - Combined hyperlipidemia - Lecithin cholesterol acyltransferase deficiency - Tangier disease - Abetalipoproteinemia - Smith-Lemli-Opitz syndrome
Cu Wilson's disease/Menkes disease - Fe Haemochromatosis, Aceruloplasminemia, Atransferrinemia - Zn Acrodermatitis enteropathica - PO43− Hypophosphatemia/Hypophosphatasia - Mg2+ Hypermagnesemia/Hypomagnesemia - Ca2+ Hypercalcaemia/Hypocalcaemia/Disorders of calcium metabolism - Biotin Biotinidase deficiency
and acid-base balance
Electrolyte disturbance - Na+ Hypernatremia/Hyponatremia - Acidosis (Metabolic, Respiratory, Lactic) - Alkalosis (Metabolic, Respiratory) - Mixed disorder of acid-base balance - H2O Dehydration/Hypervolemia - K+ Hypokalemia/Hyperkalemia - Cl− Hyperchloremia/Hypochloremia
|Purine and pyrimidine||
Dihydropyrimidine dehydrogenase deficiency - Hyperuricemia - Lesch-Nyhan syndrome - Purine nucleoside phosphorylase deficiency - Xanthinuria
Unconjugated (Lucey-Driscoll syndrome, Gilbert's syndrome, Crigler-Najjar syndrome) - Conjugated (Dubin-Johnson syndrome, Rotor syndrome)
Mucopolysaccharidosis - 1:Hurler/Hunter - 3:Sanfilippo - 4:Morquio - 6:Maroteaux-Lamy - 7:Sly
Mucolipidosis - I-cell disease - Pseudo-Hurler polydystrophy - Aspartylglucosaminuria - Fucosidosis - Alpha-mannosidosis - Sialidosis
- fr:Leucodystrophie métachromatique
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