Leukodystrophy refers to progressive degeneration of the white matter of the brain due to imperfect growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fiber. Myelin, which lends its color to the white matter of the brain, is a complex substance made up of at least ten different chemicals.
The leukodystrophies are a group of disorders that are caused by genetic defects in how myelin produces or metabolizes these chemicals. Each of the leukodystrophies is the result of a defect in the gene that controls one (and only one) of the chemicals. Specific leukodystrophies include:
- Metachromatic leukodystrophy
- Krabbé disease
- Pelizaeus-Merzbacher disease
- Canavan disease
- Childhood Ataxia with Central Nervous System Hypomyelination or CACH (also known as Vanishing White Matter Disease)
- Alexander disease
- Refsum disease
- Cerebrotendinous xanthomatosis
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.
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.
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
- Ability to eat
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.
The prognosis for the leukodystrophies varies according to the specific type of leukodystrophy.
Treatment for most of the leukodystrophies is symptomatic and supportive, and may include medications, physical, occupational, and speech therapies; and nutritional, educational, and recreational programs. Bone marrow transplantation is showing promise for a few of the leukodystrophies.