Metachromatic leukodystrophy (MLD) is a genetic disorder caused by a deficiency of the enzyme arylsulfatase A. It is one of a group of genetic disorders called the leukodystrophies that affect growth of the fatty covering which acts as an insulator on nerve fibers in the brain (myelin sheath). The three forms of MLD are:
Late infantile form. Often times, the onset of symptoms begins between ages 6 months and 2 years. The infant is usually normal at birth, but eventually loses previously gained abilities. Symptoms include low muscle tone (hypotonia), speech abnormalities, loss of mental abilities, blindness, uncontrolled muscle tightness (rigidity), convulsions, impaired swallowing, paralysis, and dementia.
Juvenile form. Symptoms may begin between ages 4 and 14 and include impaired school performance, mental deterioration, lack of muscle control(ataxia), twitching or shaking(seizures), and decreased memory (dementia).
Adult form. Symptoms begin after age 16 and may include impaired concentration, depression, psychiatric disturbances, ataxia, tremor, and dementia. Seizures may occur in the adult form, but are less common than in the other forms.
In all three forms, mental deterioration is usually the first sign.
There is no cure for MLD. Bone marrow transplantation may delay progression of the disease in some cases. Other treatment is symptomatic and supportive.