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Metachromatic leukodystrophy
Classification & external resources

ICD-10	E75.2
ICD-9	330.0
OMIM	250100
DiseasesDB	8080
eMedicine	ped/2893

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 .

Contents 1 Causes 2 Symptoms and forms 3 Treatment 4 See also 5 External links

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.

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 [1]
• 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.
• GeneTests at NIH/UW mld

v • d • e Metabolic pathology (E70-90)
Amino acid	Phenylketonuria - Alkaptonuria - Ochronosis - Tyrosinemia - Maple syrup urine disease - Propionic acidemia - Methylmalonic acidemia - Isovaleric acidemia - Primary carnitine deficiency - Cystinuria - Cystinosis - Hartnup disease - Homocystinuria - Citrullinemia - Hyperammonemia - Glutaric acidemia type 1
Carbohydrate	Lactose intolerance - Glycogen storage disease (type I, type II, type III, type IV, type V, type VI), Fructose intolerance, Galactosemia
Lipid	Lipid storage disorders Sphingolipidoses: Gangliosidosis - GM2 gangliosidoses (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 Neuronal ceroid lipofuscinosis (Batten disease) - Cerebrotendineous xanthomatosis - Cholesteryl ester storage disease (Wolman disease) Hyperlipidemia - Hypercholesterolemia - Familial hypercholesterolemia - Xanthoma - Combined hyperlipidemia - Lecithin cholesterol acyltransferase deficiency - Tangier disease - Abetalipoproteinemia
Mineral	Cu Wilson's disease/Menkes disease - Fe Haemochromatosis - Zn Acrodermatitis enteropathica - PO43− Hypophosphatemia/Hypophosphatasia - Mg2+ Hypermagnesemia/Hypomagnesemia - Ca2+ Hypercalcaemia/Hypocalcaemia/Disorders of calcium metabolism
Fluid, electrolyte 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
Porphyrin and bilirubin	Acatalasia - Gilbert's syndrome - Crigler-Najjar syndrome - Dubin-Johnson syndrome - Rotor syndrome - Porphyria (Acute intermittent porphyria, Gunther's disease, Porphyria cutanea tarda, Erythropoietic protoporphyria, Hepatoerythropoietic porphyria, Hereditary coproporphyria, Variegate porphyria)
Glycosaminoglycan	Mucopolysaccharidosis - Hurler syndrome - Hunter syndrome - Sanfilippo syndrome - Morquio syndrome
Glycoprotein	I-cell disease - Pseudo-Hurler polydystrophy - Aspartylglucosaminuria - Fucosidosis - Alpha-mannosidosis - Sialidosis
Other	Alpha 1-antitrypsin deficiency - Cystic fibrosis - Familial Mediterranean fever - Lesch-Nyhan syndrome