Metachromatic leukodystrophy (MLD) is a lysosomal storage disease that arises from a deficiency of the enzyme arylsullipidase (ASA). This deficiency results in buildup of sulftatides (a type of lipid) in the white matter of the central nervous system, causing demyelination (destruction of the myelin sheath, the protective cover of nerves in the brain and spinal cord).

Demyelination causes a breakdown in communication between the nerves and the brain, leading to paralysis, blindness, seizures, and eventually, death.

There are three types of MLD based on the onset of symptoms: late infantile, juvenile, and adult. Each type displays differences in enzyme activity, age of onset, and types of symptoms. 1

MLD’s worldwide incidence is estimated at 1 in 40,000 to 160,000 live births. 1


1 Types and Symptoms of Metachromatic Leukodystrophy. Brave Community. Shire International