Canavan disease is a severe, progressive disease that causes deterioration of the central nervous system resulting in very poor muscle tone, large head size, significant developmental delay, seizures, and feeding difficulties. Symptoms of Canavan disease may develop at different ages, but babies are often diagnosed around 3 to 5 months of age. Life expectancy varies. Some children die in early childhood, while others live into their teens or early twenties.

Canavan disease is caused by the deficiency of an enzyme, called aspartoacylase. Without this necessary enzyme, a substance (called N-acetylaspartic acid) builds up and damages the brain, resulting in the features of Canavan disease.

One in 40 individuals of Ashkenazi Jewish ancestry is a carrier of Canavan disease. Because of this high carrier rate, the American College of Medical Genetics (ACMG) and the American College of Obstetrics and Gynecology (ACOG) recommend Canavan carrier screening for all Ashkenazi Jewish individuals.

How Is Canavan 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 all of 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 Canavan disease 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 Canavan disease 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 contains the mutation. When two parents are carriers of Canavan disease:

• there is a 1 in 4 (25%) chance of having a child with Canavan disease,
• 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 carrier.

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

What This Test Tells You

This test tells whether you are a carrier of Canavan disease. It detects 98.9% of mutations for Canavan disease in individuals of Ashkenazi Jewish descent and ~60% of mutations in non-Jewish Caucasians. Specifically, it looks to see if you carry one of the four most common mutations in the ASPA gene that can cause Canavan disease. They are called E285A, Y231X, A305E, and 433-2A>G.

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