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Metachromatic leukodystrophy

Contents of this page:

Alternative Names   

MLD; Arylsulfatase A deficiency; Leukodystrophy - metachromatic

Definition    Return to top

Metachromatic leukodystrophy (MLD) is a genetic disorder that affects nerves, muscles, other organs, and behavior. It slowly gets worse over time.

Causes    Return to top

MLD is usually caused by the lack of an important enzyme called arylsulfatase A. Because this enzyme is missing, chemicals called sulfatides build up in and damage the nervous system, kidneys, gallbladder, and other organs. In particular, the chemicals damage the protective sheaths that surround nerve cells.

The disease is passed down through families (inherited). You must get a copy of the defective gene from both your parents to have the disease. Parents can each have the defective gene, but not have MLD. A person with one defective gene is called a "carrier."

Children who inherit only one defective gene from one parent will be a carrier, but usually will not develop MLD. When two carriers have a child, there is a 25% chance that the child will get both genes and have MLD.

MLD occurs in about 1 in 40,000 people. There are three forms of the disease. They are based on when the symptoms begin:

Symptoms    Return to top

Exams and Tests    Return to top

Signs include:

Possible tests include:

Treatment    Return to top

There is no cure for MLD. Care focuses on treating the symptoms and preserving the patient's quality of life with physical and occupational therapy.

Research is studying techniques to replace the missing enzyme (arylsulfatase A).

Support Groups    Return to top

For additional information and resources, see:

Outlook (Prognosis)    Return to top

MLD is a severe disease that gets worse over time. Eventually people lose all muscle and mental function. Life span varies depending on what age the condition started, but the disease course usually runs 3 - 20 or more years.

People with this disorder are expected to have a shorter-than-normal lifespan. The earlier the age at diagnosis, the more quickly the disease progresses.

Prevention    Return to top

Genetic counseling is recommended if you have a family history of this disorder.

Update Date: 10/15/2008

Updated by: Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the ABGC, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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