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 and urine tests.
This disease causes premature death.
This disease cannot be treated or cured, but treatment options are being studied.
There are different types of inherited disorders Inheritance of Single-Gene Disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more . In metachromatic leukodystrophy, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders Overview of Hereditary Metabolic Disorders Hereditary metabolic disorders are inherited genetic conditions that cause metabolism problems. Heredity is the passing of genes from one generation to the next. Children inherit their parents'... read more .)
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.
Types 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
Blood and urine 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 Chorionic Villus Sampling Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more or amniocentesis Amniocentesis Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more .
After birth, doctors do nerve conduction studies Nerve conduction studies Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more to measure the speed at which nerves conduct impulses. Blood and urine tests are also done. Doctors do the imaging tests computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (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. Genetic testing Genetic Screening Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more , 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
This disease cannot be cured at the present time. However, bone marrow transplantation or stem cell transplantation Stem Cell Transplantation Stem cell transplantation is the removal of stem cells (undifferentiated cells) from a healthy person and their injection into someone who has a serious blood disorder. (See also Overview of... read more may help people who have mild forms of the disease.
Enzyme replacement therapy and gene therapy Gene Therapy Although gene therapy is defined as any treatment that changes gene function, it is often thought of as the insertion of normal genes into the cells of a person who lacks such normal genes because... read more are possible treatment options that are being studied.