Metachromatic leukodystrophy

Injury	Disease	Nutrition	Poison

Symptoms	Surgery	Test	Special Topic

Metachromatic leukodystrophy

Definition:

Metachromatic leukodystrophy (MLD) is a genetic disorder that affects nerves, muscles, and other organs. It gets progressively worse over time.

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MLD is usually caused by the lack of an important enzyme called arylsulfatase A. Because this enzyme is missing, chemicals called sulfatides accumulate in the nervous system, kidneys, gallbladder, and other organs. The sulfatides damage the nerves and organs where buildup occurs. In particular, it damages the myelin sheaths that surround nerve cells.

There are three forms, based on when the symptoms begin:

Late infantile -- symptoms usually begin by age 4. The symptoms include problems walking, loss of muscle control, and loss of mental functions.
Juvenile -- symptoms begin between 4 and 6 years old. The child has trouble walking and loses developmental milestones. The first sign may be deteriorating school performance.
Adult -- the late juvenile (age 6-16 age) and adult (over age 16) forms progress slowly. Early signs may be behavior problems, loss of mental functions, poor school or work performance, seizures, and loss of muscle control.

Alternative Names:
MLD; Arylsulfatase A deficiency
Causes, incidence, and risk factors:

Metachromatic Leukodystrophy is caused by a mutation in the gene that makes arylsulfatase A. The disease is inherited as an autosomal recessive genetic disorder. This means that an affected person inherits a copy of the defective gene from both parents. A person who inherits a defective gene from only one parent is usually not affected.

When two "carrier" (unaffected) parents have a child, there is a 25% chance that the child will inherit the gene from both parents. If that happens, the child will have MLD.

Metachromatic Leukodystrophy occurs in about 1 per 40,000 people.