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Metachromatic Leukodystrophy - Video

The animated videos in NORD’s Rare Disease Video Library provide brief introductions to rare disease topics for patients, caregivers, students, professionals and the public. NORD collaborates with medical experts, patient organizations, videographers and Osmosis to develop the videos, which are made possible by individual donations, educational grants and corporate sponsorships. NORD is solely responsible for the content.

General Discussion


Metachromatic leukodystrophy (MLD) is a rare hereditary disease characterized by accumulation of fats called sulfatides. This causes the destruction of the protective fatty layer (myelin sheath) surrounding the nerves in both the central nervous system and the peripheral nervous system. There are three types of MLD based on the age symptoms appear: late-infantile MLD, juvenile MLD, and adult MLD. All subtypes ultimately affect both intellectual and motor function. Symptoms vary by type but can include difficulty talking, seizures, difficulty walking, personality changes, and behavior and personality changes. MLD is caused by changes (mutations) in the ARSA gene and, in rare cases, the PSAP gene.


This condition is called metachromatic leukodystrophy because when viewed under a microscope, sulfatide accumulation in cells appears as granules that are colored differently than other cellular material (metachromatic). A leukodystrophy is a genetic disorder that disrupts myelination in the brain.

Synonyms of Metachromatic Leukodystrophy

  • MLD
  • diffuse brain sclerosis
  • metachromatic leukoencephalopathy
  • ARSA deficiency
  • arylsulfatase A deficiency

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