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Testing for Genetic Disorders

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Ashkenazi Jewish Genetic Conditions

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ASHKENAZI JEWISH CARRIER TESTING

Maple Syrup Urine Disease, Types 1a and 1b

Maple Syrup Urine Disease (MSUD) can cause feeding problems, brain damage, coma, and death if the condition isn't treated starting in infancy. Individuals with MSUD can be treated with changes in diet and careful monitoring. Even those who are treated may sometimes have problems during times of stress or infection. It is important that MSUD be diagnosed and treated very soon after birth to prevent brain damage and other neurological problems. For this reason, many states include MSUD in their mandatory newborn screening programs that screen all newborns at birth. Individuals with MSUD have a distinctive maple syrup smell to their urine and earwax which is how the condition got its name.

MSUD is more common in individuals of Ashkenazi Jewish descent and certain Mennonite populations.

About 1 in 81 people (1.2%) with Ashkenazi Jewish ancestry are carriers of MSUD. In some Mennonite populations, up to 1 in 10 (10%) people may be carriers.

How is Maple Syrup Urine Disease Inherited?

The cells in our body typically contain 46 chromosomes. Each chromosome is a package that holds hundreds of genes. These genes contain the blueprints for our growth and development; they are the instructions that make us who we are. All of our chromosomes (and the genes that are located on these chromosomes) come in pairs. We inherit one chromosome of each pair from our mother and the other chromosome of the pair from our father. When there is a change in a gene (called a mutation) the instructions it contains are no longer correct and the gene cannot carry out its function.

Individuals with MSUD have two copies of a mutation, one copy inherited from each parent. Neither gene in the pair is working correctly, which causes the symptoms of the disease.

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A carrier of MSUD is a person who has a mutation in one gene of the pair. Carriers are unaffected with the disease because the properly working gene is able to compensate for the gene that has the mutation.

When two parents are carriers of MSUD:

there is a 1 in 4 (25%) chance of having a child with MSUD,
there is a 1 in 2 (50%) chance of having a child who is an unaffected carrier like the parents,
and, there is 1 in 4 (25%) chance of having a child who is unaffected and is not a carrier.

When one parent is a carrier of MSUD and the other parent is not a carrier, the parents are not at increased risk to have a child with MSUD. Instead, there is a 1 in 2 (50%) chance of having a child who is an unaffected carrier like the one parent.

What This Test Tells You

This test tells you if you are a carrier for Maple Syrup Urine Disease. The test looks for four mutations (Y438N, R183P, G278S, and E372X) in the E1 alpha subunit and E1 beta subunit of the branched-chain ketoacid dehydrogenase complex. These mutations are common in the Ashkenazi Jewish and Mennonite populations, but not in people from other ethnic groups. The chance that a mutation will be found if it exists in the gene is called the "detection rate". The detection rate in the Ashkenazi Jewish and Mennonite populations is 99%. When no mutation is found, the result reduces the chance that you are a carrier of MSUD but it does not eliminate the chance. This test only detects MSUD, types 1a and 1b. It doesn't detect other forms of MSUD.

How Testing Works

Testing with DNA Direct is quick, convenient, and can be done in the privacy of your home. It can also be anonymous if you wish. How to order online and consult with our genetic experts: DNA Direct's Expert Services

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