What Causes MLD

MLD is caused by the inability to break down sulfatide - a fatty substance normally present in the brain. Scientists have traced the development of MLD to a defect in the gene that tells the body how to make an enzyme called arylsulfatase A or (ASA). This is the enzyme responsible for breaking down sulfatide into smaller, harmless chemicals that can be eliminated or reused by the body.

In MLD, the lack of proper ASA enzyme leads to a buildup of sulfatide, which causes a process called demyelination . The demyelination causes the symptoms of MLD by affecting communication between nerves in the brain.
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Nerves work like a system of electrical connections. Axons - or tiny stands similar to electrical wires - run from one nerve to another, carrying electrical messages. Like electrical wires, the axons are wrapped with an insulating material. The insulating material around axons is called myelin. Ordinarily, special cells in the brain called oligodendrocytes insulate, or myelinate, the axons. In MLD, however, sulfatide accumulates and interferes with the oligodendrocytes' myelination of the axons. The axons lose their myelin insulation, - or demyelinate. Without the proper insulation, the nerves "short circuit" and cannot communicate.

Leukodystrophy Facts

The leukodystrophies are inherited, progressive, non-selective disorders of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). They include the following:

• Metachromatic Leukodystrophy (MLD)
• Adreno Leukodystrophy (ALD)
• Krabbe's Disease
• Canavan's Disease
• Alexander's Disease
• Pelizaeus-Merzbacher Disease
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