A Family Guide to Non-Oncologic Blood Disorders
Metachromatic Leukodystrophy
What is metachromatic leukodystrophy? Metachromatic leukodystrophy (MLD) is one of a group of ge- netic disorders called the leukodystrophies. Breaking down the words reveals the definition. “Meta” means change, “chromat- ic” means color, “leuko” means white matter, and “dystrophy” means degeneration. MLD is caused by a deficiency of the enzyme arylsulfatase A. When the enzyme is missing, there is a toxic buildup of abnormal fatty materials (lipids), which causes destruction of the myelin sheath. The myelin sheath is the protective covering around the nerves that carry signals from the brain to the various parts of the body. When the myelin sheath is damaged, the brain cannot communicate with other parts of the body, such as the muscles, eyes, mouth, and other parts of the brain. MLD is a disorder that a person inherits from a defective gene from both parents. There are three forms of MLD: late infantile, juvenile, and adult. Late infantile is the most common form of MLD. What are some symptoms of MLD? The following are the most common symptoms of MLD. How- ever, each child may experience symptoms differently. Late infantile MLD symptoms typically begin around 12–20 months after birth and include: • Difficulty walking after the first year of life • Muscle wasting, weakness, and rigidity • Developmental delays • Progressive loss of vision leading to blindness • Convulsions (the muscles contract and relax rapidly and very often, which causes the body to shake uncontrollably) • Impaired swallowing • Paralysis (loss of muscle function in one or more muscles) • Memory loss • If untreated, most children with MLD do not survive past the age of 5.
Juvenile MLD symptoms begin between 3–10 years old and include: • Impaired school performance • Mental deterioration • Dementia, which leads to symptoms similar to late infantile MLD but have a slower progression • Death occurs 10 to 20 years following onset of symptoms. Adult MLD symptoms begin after age 16 and include: • Symptoms similar to depression or other types of men- tal illness • Impaired concentration • Ataxia (lack of coordination of muscles) • Seizures • Tremors • Progressive memory loss • Death occurs 6–14 years following onset of symptoms. How is MLD diagnosed? • Diagnosis is made through magnetic resonance imag- ing (MRI), an imaging test that uses powerful magnets to help create images of the organs and tissues in the body. • Blood and urine tests determine deficiency of the miss- ing enzyme. What tests and procedures will my child need? • Imaging studies of the brain using an MRI are per- formed in most cases. An MRI scan usually will show an unusual decrease in white matter due to loss of myelin. • A blood test is done to check for enzyme levels and a urine test confirms the presence of sulfatides (a major fat component of the myelin sheath).
Metachromatic Leukodystrophy
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