Metachromatic Leukodystrophy (MLD) is a rare genetic disorder that affects the nervous system. It is caused by a deficiency of the enzyme arylsulfatase A, which leads to the accumulation of sulfatides in the body. This buildup damages the myelin sheath, the protective covering of nerve fibers, resulting in progressive neurological decline. Symptoms of MLD can vary but often include loss of motor skills, difficulty walking, and cognitive decline. The condition typically manifests in childhood, but there are also late-onset forms. Diagnosis is usually confirmed through genetic testing and enzyme activity assays.