Metachromatic leukodystrophy

Definition:

Metachromatic leukodystrophy is an inherited metabolic storage disease characterized by the absence of the enzyme arylsulfatase A and increased storage of sulfatide.

Alternative Names:

MLD; Arylsulfatase A deficiency

Causes, incidence, and risk factors:

Metachromatic leukodystrophy (MLD) is transmitted as an autosomal recessive trait. MLD has a wide range of symptoms. As with many other storage diseases, there are forms of early and delayed onset (late infant, juvenile and adult types). The most common (and the most severe form) is the late infant onset form, which has symptoms such as irritability, decreased muscle tone, muscle wasting, the loss of the ability to walk. Debility is progressive with blindness, seizures, and partial paralysis. Death occurs usually before age 10.

Both the juvenile and adult forms have later onset but similar symptoms. In the adult and juvenile forms, psychosis and emotional disturbances are an important part of the illness. The juvenile form is fatal within a few years of diagnosis. The adult form may be drawn out over many years.

Symptoms:

irritability
decreased muscle tone
abnormal high muscle tone, spasm, abnormal muscle movements
falls frequently
decreased intellectual functioning
speech difficulties, slurring
feeding difficulties
swallowing difficulty
nerve function abnormality

Signs and tests:

decreased or absent deep tendon reflexes
nystagmus (abnormal eye movements)
poor visual fixation
optic nerve atrophy
decorticate posturing
coma

Tests:

nerve velocity conduction studies
MRI
CT scan
lumbar puncture and examination of the cerebrospinal fluid showing increased CSF total protein
nerve biopsy (usually performed on the sural nerve) showing metachromatic deposits
urine chemistry showing markedly increased sulfatide levels
urinalysis showing metachromatic granules in the urine sediment
culture of skin fibroblasts or white blood cells for decreased arylsulfatase A activity

Treatment:

At present, there is no treatment for metachromatic leukodystrophy itself. Symptomatic treatments may provide mild relief.

Support Groups:

The United Leukodystrophy Association can be reached at http://www.ulf.orgwww.ulf.org.

Expectations (prognosis):

Metachromatic leukodystrophy is a severely debilitating progressive disease whose outcome is fatal.

Complications:

bronchopneumonia

Calling your health care provider:

Call your health care provider if you have a family history of this disease or if you notice symptoms suggestive of this disorder.

Prevention:

Genetic counseling is recommended for parents with a family history of metachromatic leukodystrophy.

Review Date: 8/31/2001
Reviewed By: David G. Brooks, M.D., Ph.D., Division of Medical Genetics, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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