What is MLD?
Metachromatic leukodystrophy is a genetic disorder that affects nerves, muscles, and other organs. It gets progressively worse over time. MLD is usually caused by the lack of an important enzyme called arylsulfatase A. Because this enzyme is missing, chemicals called sulfatides accumulate in the nervous system, kidneys, gallbladder, and other organs. The sulfatides damage the nerves and organs where buildup occurs. In particular, it damages the myelin sheaths that surround nerve cells.
There are three forms of MLD, defined by the age of onset of the disease. The late infantile form of MLD is the most common, and produces symptoms between the ages of 1 and 2. The juvenile form generally becomes apparent between the ages of 4 and 12, and the adult form occurs after age 14. As with all the leukodystrophies, the symptoms can vary widely, although in all cases there is a progressive loss of physical and intellectual function over a relatively extended period of time. In general, the earlier the onset, the more rapid the progression of the disease.
Currently, the only treatment for MLD is bone marrow transplantation; this means that cells that produce normal ASA are introduced into the patient, and the normal ASA protein is then taken up into the deficient cells, allowing sulfatides in those cells to be broken down. However, this is only useful for those who are pre-symptomatic or those with very mild neurological manifestations.
Links
United Leukodystrophy Foundation
The Myelin Project Stennis Foundation