Leukodystrophy

Leukodystrophy refers to a group of disorders characterized by progressive degeneration of the white matter of the brain. The leukodystrophies are caused by imperfect growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fibers. Myelin, which lends its color to the white matter of the brain, is a complex substance made up of at least ten different molecules. Each of the leukodystrophies is the result of a defect in the gene that controls the production or metabolism of one (and only one) of the component molecules of myelin.

The word leukodystrophy comes from the Greek roots leuko, white, dys, lack of, and troph, growth. Thus leukodystrophy describes a set of diseases that affect the growth or maintenance of the white matter.

Types
Specific leukodystrophies include (ICD-10 codes are provided where available):
 * (E71.3) adrenoleukodystrophy
 * (E75.2) metachromatic leukodystrophy
 * (E75.2) Krabbe disease
 * (E75.2) Pelizaeus-Merzbacher disease
 * Canavan disease
 * childhood ataxia with central hypomyelination (CACH or vanishing white matter disease)
 * Alexander disease
 * (G60.1) Refsum disease
 * cerebrotendineous xanthomatosis

Cause
Leukodystrophies are mostly inherited disorders, meaning that it is passed on from parent to child. They may be inherited in a recessive, dominant, or X-linked manner, depending on the type of leukodystrophy. The individual pages on each leukodystrophy will describe the particular pattern of inheritance for that disease. There is also a separate fact sheet describing the different genetic inheritance patterns available from the United Leukodystrophy Foundation.

There are some leukodystrophies that do not appear to be inherited, but rather arise spontaneously. They are still caused by a mutation in a particular gene, but it just means that the mutation was not inherited. In this case, the birth of one child with the disease does not necessarily increase the likelihood of a second child having the disease.

Symptoms
The most common symptom of a leukodystrophy disease is a gradual decline in an infant or child who previously appeared well. Progressive loss may appear in body tone, movements, gait, speech, ability to eat, vision, hearing, and behavior. There is often a slowdown in mental and physical development. Symptoms vary according to the specific type of leukodystrophy, and may be difficult to recognize in the early stages of the disease.

Current research
One source of active (as of 2006) research is The Myelin Project.