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WHAT IS METACHROMATIC LEUKODYSTROPHY?

Metachromatic leukodystrophy is a type of metabolic disorder that leads to a deadly build up of fats (known as lipids) in the body and the destruction of myelin. Myelin is a fatty nerve covering that sends impulses quickly. A metabolic disorder means that there is some type of impairment in metabolism. Metabolism is a term for the chemical actions in cells that release energy from nutrients or that use energy to create other substances. A cell is the smallest, most basic unit of life, that is capable of existing by itself.

Metachromatic leukodystrophy is an inherited disorder, meaning that it is passed on to the child from the parents' genes. Genes are units of material contained in a person's cells that contain coded instructions as for how certain bodily characteristics (such as eye color) will develop. All of a person's genes come from his/her parents. Genes are contained in structures called chromosomes. Each person has 23 pairs of chromosomes.

In metachromatic leukodystrophy, chromosome 22 is dysfunctional because it is missing an enzyme known as arylsulfatase. An enzyme is a type of protein that helps produce chemical reactions in the body. Without the enzyme, arylsulfatase, a build up of metachromatic lipids occurs in the body. Metachromatic lipids are fatty substances that have changed colors. The technical name for the type of metachromatic lipids that build up in this condition is called galactosyl sulfatidates.

The metachromatic lipids build up in the brain, spine, the peripheral nerves (nerves outside of the brain and spine), liver, spleen, and other organs. The liver is the largest organ in the body and is responsible for filtering (removing) harmful chemical substances, producing important chemicals for the body, and other important functions. The spleen is an organ next to the stomach that helps fight infections and removes and destroys worn-out red blood cells. Red blood cells help carry oxygen in the blood.

A buildup of metachromatic lipids leads to the destruction of myelin (see first paragraph for description). In metachromatic leukodystrophy, the myelin is destroyed in the brain, spine, and the peripheral nerves (nerves outside of the brain and spine). In the brain, the myelin is widely destroyed in the cerebrum (the top section of the brain) and the cerebellum (a part in the back lower area of the brain important for movement). It should be noted that a defect on the 10th chromosome is also thought to lead to metachromatic leukodystrophy.

WHAT AGE DO PEOPLE USUALLY GET METACHROMATIC LEUKODYSTROPHY?

Metachromatic leukodystrophy usually occurs in infancy between ages 1 and 4. It usually begins at age 2. However, there is an adult form of the condition.

HOW MANY PEOPLE ARE BORN WITH METACHROMATIC LEUKODYSTROPHY?

In approximately 1 in every 100,000 births, there will be someone who develops metachromatic leukodystrophy

WHAT ARE SIGNS AND SYMPTOMS OF METACHROMATIC LEUKODYSTROPHY?

Signs and symptoms of metachromatic leukodystrophy are deterioration of the brain, mental decline, and mental retardation. More signs and symptoms include intention tremor (uncontrollable shaking movements that occur when trying to complete an action), convulsions (abnormal, severe, involuntary muscle movements), vision impairment, decreased reflexes, reduced speech production, squinting of the eyes, nystagmus (rhythmic involuntary jerking or swinging movements of the eyes), spastic gait (an abnormal type of walking with weak, stiff legs), and worsening paralysis. Paralysis is loss of movement and/or sensation.

In adults with metachromatic leukodystrophy, dementia and psychosis occur. Dementia is a mental disorder characterized by a significant loss of intellectual and cognitive abilities without impairment of perception or consciousness. Psychosis is a mental disorder characterized by an impaired ability to understand reality.

WHAT IS THE PROGNOSIS FOR PEOPLE WITH METACHROMATIC LEUKODYSTROPHY?

Most people with metachromatic leukodystrophy die between ages 5 and 10.

WHAT ELSE IS METACHROMATIC LEUKODYSTROPHY KNOWN AS?

Metachromatic leukodystrophy is also known as sulfatide lipidosis and arylsulfatase A deficiency.

WHAT IS THE ORIGIN OF THE TERM, "METACHROMATIC LEUKODYSTROPHY"?

Meta is Greek for "after, between, and over," and is a word used to mean "a change." Chromatic "comes from the Greek word "chroma" meaning "color." Leuko comes from the Greek word "leukos" meaning "white." In this case, white refers to white matter (white substance) of the brain and spine. Dys is Greek for "bad," and "trophy" comes from the Greek word "trophe" meaning "nourishment." Put the words together and you have "a change in color and bad nourishment of the white matter" (of the brain and spine).