MedFriendly®
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.
FEATURED BOOK: Inborn Metabolic Disease: Diagnosis and Treatment
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.
"Where Medical Information is Easy to Understand"™
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.
HOW IS METACHROMATIC LEUKODYSTROPHY TREATED?
There is no cure for metachromatic leukodystrophy. However, bone marrow transplants have been known
to slow disease progress. Bone marrow is a tissue that fills the openings inside of bones and helps create
red blood cells. Red blood cells carry oxygen in the body.
The general goal of treatment of metachromatic leukodystrophy is to reduce signs and symptoms to
improve quality of life. Treatment includes use of pain medications, speech therapy, occupational therapy
to improve activities of daily living, and physical therapy to improve muscle and joint mobility, range of
motion, and flexibility. If swallowing becomes difficult, a nutritionist can provide assistance on the best
way to obtain nutrition. Assistive feeding devices may be needed at some point.
WHAT IS THE PROGNOSIS IN 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).
