Metachromatic leukodystrophy (MLD) is a rare and devastating genetic disorder that primarily affects the nervous system. Translated from doctor talk MLD means: meta - change, chromatic - color, leuko-white matter, dystrophy - degeneration. It is characterized by a deficiency of the enzyme arylsulfatase A (ARSA), which leads to the accumulation of a substance called sulfatide in various tissues, particularly in the white matter of the brain and the peripheral nerves. This buildup of sulfatide disrupts the normal formation and maintenance of the protective myelin sheath around nerve cells, causing progressive and severe neurological deterioration. 

MLD typically manifests in early childhood and progresses rapidly, leading to a range of symptoms such as muscle weakness, loss of motor skills, cognitive decline, and ultimately, a complete loss of physical and mental function. Unfortunately, there is no cure for MLD, and treatment options are limited to palliative care to manage symptoms and improve the quality of life for affected individuals.