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Metachromatic leukodystrophy (MLD) caused by arylsulfatase A deficiency is a lysosomal storage disorder that is characterized by leukodystrophy and progressive neurologic dysfunction. Approximately 50-60% of patients have the late-infantile form with onset usually between one and two years, 20-30% of patients have the juvenile form with onset between 4 years and puberty, and 15-20% of patients have the adult form. The late-infantile form is the most severe with loss of previously acquired skills, optic atrophy, ataxia, dementia, seizures and spastic quadriparesis. In the juvenile form, the initial symptoms are usually declining school performance and the onset of behavioral problems. Clumsiness, gait problems, slurred speech, incontinence, bizarre behavior and seizures are also observed. In some adult patients, problems in school and/or work performance, personality changes and emotional lability may be presenting symptoms, and in others neurologic symptoms including weakness, loss of coordination, seizures and peripheral neuropathy may be the first signs of disease. All forms eventually result in the complete loss of motor and intellectual functions with the disease course ranging from 3-10 years in the late- infantile form and up to 20 years in the juvenile and adult forms. Life span is usually inversely correlated with the age of onset. The disease prevalence is estimated at between 1 in 40,000 to 1 in 160,000 with a higher prevalence in some populations including Habbanite Jews in Israel, Israeli Arabs, Christian Israeli Arabs and the Navajo Nation in the United States.
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Zou et al. Whole exome sequencing: an effective and comprehensive genetic testing approach for leukodystrophy [abstract submitted] To be presented at the 2017 ASHG Annual Genetics Meeting, October 17-21, Orlando, FL.