描述
Metachromatic leukodystrophy (MLD) is caused by a defect in the ARSA gene which does for arylsulfatase A. A defect in this enzyme results in accumulation of 3-O-sulfogalactosylceramide in urine, neural and non neural tisues like kidney and gallbladder. There are several forms of MLD. In the late infantile form, which is the most common form MLD, affected children begin having difficulty walking after the first year of life. Symptoms include muscle wasting and weakness, muscle rigidity, developmental delays, progressive loss of vision leading to blindness, convulsions, impaired swallowing, paralysis, and dementia. Children may become comatose. Untreated, most children with this form of MLD die by age 5, often much sooner. Children with the juvenile form of MLD (onset between 3–10 years of age) usually begin with impaired school performance, mental deterioration, and dementia and then develop symptoms similar to the late infantile form but with slower progression. Age of death is variable, but normally within 10 to 15 years of symptom onset. The adult form commonly begins after age 16 as a psychiatric disorder or progressive dementia. Adult-onset MLD progresses more slowly than the late infantile and juvenile forms, with a protracted course of a decade or more.