Metachromatic leukodystrophy

Who might consider genetic carrier testing for a family history of metachromatic leukodystrophy?

If someone has a family history of metachromatic leukodystrophy (MLD) or someone is known to be a carrier for MLD, individuals who are biologically related to the affected individual or carrier are at risk to be a carrier. Generally speaking, the more closely related an individual is to the affected individual or carrier, the greater the chance for that person to be a carrier. Prior to genetic testing, the chance to be a carrier for some biological relatives of an affected individual are as follows:

  • Parent of affected individual: assumed to be 100% (called an obligate carrier)
  • Unaffected sibling of affected individual: 2 in 3 (~66.6%)
  • Aunt or uncle of affected individual: 1 in 2 (50%)
  • First cousin of affected individual: 1 in 4 (25%)

If someone has carrier testing and is found to be negative (not a carrier), that person's children are typically assumed to be negative also.

More information about the use of genetic carrier testing is available on GeneTests' Web site and can be viewed by clicking here.

Individuals who are interested in learning about genetic testing and about their specific risk to be a carrier should speak with a genetics professional.

Last updated on 05-01-20

How is metachromatic leukodystrophy inherited?

Metachromatic leukodystrophy is inherited in an autosomal recessive manner. This means that both copies of the disease-causing gene in each cell must have a mutation for an individual to be affected. Individuals inherit two copies of each gene - one copy from each parent. Typically, an individual is affected because they inherited a mutated copy of the gene from each parent. Individuals with one mutated copy of the gene (such as an unaffected parent of an affected individual) are referred to as carriers; carriers typically do not have any signs or symptoms of the condition.

When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) chance to have the condition, a 50% (1 in 2) chance to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.

Last updated on 05-01-20

Is someone is a carrier for metachromatic leukodystrophy, what are the chances for his/her siblings to be carriers?

Each sibling of a carrier for metachromatic leukodystrophy (MLD) has a 50% chance to also be a carrier. A carrier for MLD has one mutated copy of the disease-causing gene in each cell (as well as one normal copy). Typically, a carrier will have inherited the mutated copy from a carrier parent. A carrier parent, who also has one mutated copy and one normal copy of the gene, will randomly pass one of these copies on to each child. Therefore, at conception, each child of a carrier has a 50% (1 in 2) chance inherit the mutated copy and be a carrier, and a 50% chance to inherit the normal copy and not be a carrier.

Last updated on 05-01-20

What is the prognosis for individuals with metachromatic leukodystrophy?

The prognosis for metachromatic leukodystrophy (MLD) is poor. The late infantile form of the disorder, the most common type, usually appears in the second year of life. This form typically progresses over approximately 5 to 10 years. Most children with the infantile form die by age 5. The juvenile form, with onset between the age of 4 and adolescence, has a slower progression than the late infantile form and symptoms may develop over 10 to 20 years; death typically occurs 10 to 20 years following onset. In the adult form, the first symptoms typically appear during the teenage years or later. This form may possibly progress over 20 to 30 years, although many individuals with the adult form die within 6 to 14 years following the onset of symptoms. During the progression of this form there may be some periods of relative stability and other periods of more rapid decline.

Last updated on 05-01-20

Name: United Leukodystrophy Foundation (ULF) 224 North Second Street Suite 2
DeKalb, IL, 60115 , United States
Phone: 815-748-3211 Toll Free: 800-728-5483 Fax : 815-748-0844 Email: Url:
Name: MLD Foundation 21345 Miles Drive
West Linn, OR, 97068-2878, United States
Phone: 503-656-4808 Toll Free: 800-617-8387 Fax : 503-212-0159 Email: Url:
Name: Alex The Leukodystrophy Charity Alex TLC 45 Peckham High Street
London, SE15 5EB, United Kingdom
Phone: 020 7701 4388 Email: Url:
Name: European Association against Leukodystrophy ELA 2, rue Mi-les-Vignes BP 61024 54521
Laxou Cedex
Email: Url:
Name: The Calliope Joy Foundation PO Box 2866
Bala Cynwyd, PA, 19004,
Phone: 610-664-1588 Email: Url:

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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