Metachromatic leukodystrophy is a type of lysosomal storage disorder called a sphingolipidosis. It is caused by a buildup of fats (lipids) in the brain, spinal cord, kidneys, and spleen. This disorder results in early death. Metachromatic leukodystrophy occurs when parents pass on to their children the defective genes that cause this disorder.
Metachromatic leukodystrophy occurs when the body lacks enzymes needed to break down a certain lipid.
Symptoms vary depending on whether the child has the infantile form or the juvenile form but may include paralysis, dementia, and nerve problems.
The diagnosis may be made by doing prenatal screening tests, nerve conduction studies, and blood tests.
This disorder cannot be treated, but treatment options are being studied.
There are different types of inherited disorders. In metachromatic leukodystrophy, both parents of the affected child carry 1 copy of the abnormal gene. Because usually 2 copies of the abnormal (recessive) gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders.)
Sphingolipidoses occur when people do not have the enzymes needed to break down (metabolize) sphingolipids, which are compounds that protect the cell surface and serve certain functions in the cells. There are many types of sphingolipidoses besides metachromatic leukodystrophy.
In metachromatic leukodystrophy, an enzyme needed to break down a certain lipid, called arylsulfatase A, is not working correctly. This lipid builds up in the white matter of the brain and spinal cord, nerves, kidneys, spleen, and other organs. This buildup results in demyelination. Demyelination is the destruction of the tissue that wraps around nerves, called the myelin sheath. When the myelin sheath is damaged, nerves do not conduct electrical impulses normally. When impulses are not conducted normally, movements are jerky, uncoordinated, and awkward.
Forms of Metachromatic Leukodystrophy
In the infantile form, a child has progressive paralysis and dementia, meaning that the paralysis and dementia get worse throughout the life of the child. Symptoms of this form usually begin before 4 years of age and result in death by about age 9.
In the juvenile form, children have problems walking, intellectual impairment, and weakness, numbness, and pain in the hands and feet. Symptoms of this form begin between 4 years and 16 years of age.
There is also a milder adult form.
Diagnosis of Metachromatic Leukodystrophy
Prenatal screening tests
Nerve conduction studies
Computed tomography or magnetic resonance imaging
Before birth, metachromatic leukodystrophy may be diagnosed in the fetus by using the prenatal screening tests chorionic villus sampling or amniocentesis.
After birth, doctors do nerve conduction studies to measure the speed at which nerves conduct impulses. Doctors do the imaging tests computed tomography (CT) or magnetic resonance imaging (MRI) of the brain to look for signs of damage to the myelin sheaths.
Doctors also measure levels of arylsulfatase A in white blood cells or skin cells and do tests to analyze DNA. Genetic testing, which is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder, is also available.
Treatment of Metachromatic Leukodystrophy
No treatment is available at present
This disorder cannot be cured at the present time. However, bone marrow transplantation or stem cell transplantation may help people who have mild forms of the disease.
Enzyme therapies and gene therapy are possible treatment options that are being studied.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
National Organization for Rare Disorders (NORD): This resource provides information to parents and families about rare diseases, including a list of rare diseases, support groups, and clinical trial resources.
Genetic and Rare Diseases Information Center (GARD): This resource provides and easy to understand information about rare or genetic diseases.
