Leukodystrophy

Definition

Definition of Leukodystrophy
Leukodystrophy refers to a group of disorders characterized by dysfunction 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, from which the white matter of the brain takes its colour, is a complex substance made up of at least ten different chemicals. 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.

Inherited
Genes come in paired sets, with one set inherited from each parent. The leukodystrophies are almost all inherited in either an X-linked or autosomal recessive way.

1. Autosomal recessive: The child can only inherit the disorder if both parents are carriers of the gene. Boys and girls are equally affected. The carrier parents won’t have any symptoms, but each of their children will have a one in four chance of developing leukodystrophy and a one in two chance of being a carrier themselves.
2. X-linked: The gene is carried on the X chromosome, which is involved in determining the baby’s sex. Men have an X and a Y chromosome and women have two X chromosomes. Because men only have a single copy of the genetic programs on the X chromosome, if there is a genetic change, there are no other genes to compensate. Boys and girls are therefore affected differently.
3. Leukodystrophy is Different to Multiple Sclerosis: The white matter can be affected as a result of (secondary to) a number of conditions, including ischaemia, infection, other metabolic conditions and multiple sclerosis.

Symptoms

Symptoms of Leukodystrophy
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.

Causes

Causes of Leukodystrophy
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 articles 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.

Diagnosis

Diagnosis of Leukodystrophy
The diagnosis of a specific leukodystrophy is often not easy. Frequently, it will involve the input of a number of specialists, including neurologists, geneticists and metabolic physicians. In around half the cases, a named diagnosis may not be possible.

Depending on the type of leukodystrophy, diagnostic methods can include:

1. Physical examination
2. Blood tests
3. Urine tests
4. MRI scans
5. Nerve conduction tests
6. Neurocognitive tests
7. Nerve biopsy
8. Genetic tests.

Prognosis

Prognosis of Leukodystrophy
The prognosis for the leukodystrophies varies according to the specific type of leukodystrophy.

Treatment

Treatment 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.

Prevention

Prevention of Leukodystrophy
Consult with your doctor.