DOCTOR'S VIEWS ARCHIVE

Canavan Disease -- Genetic Screening Advised

The Committee on Genetics of the American College of Obstetricians and Gynecologists (ACOG) has recommended that persons of Eastern and Central European (Ashkenazi) Jewish descent be offered screening for Canavan disease, a progressive fatal genetic disorder of the central nervous system. The screening would be for the detection of carriers of the gene that causes the inherited disorder. About 90% of the six million Jews in the United States are of Ashkenazu descent and are possible carriers (see below).

When a child with Canavan disease is between 3 and 6 months of age, the signs and symptoms of the disorder usually begin to appear. These include developmental delay (significant motor slowness), enlargement of the head (macrocephaly), loss of muscle tone (hypotonia), poor head control, and severe feeding problems.

In time, as the disease progresses, there are convulsions (seizures), deterioration of the nerve to the eye (optic atrophy), blindness, heartburn (gastrointestinal reflux), and difficulties swallowing.

There is currently no effective treatment for the disease and no cure in sight. Most children with Canavan disease die before the age of 10.

Canavan disease is due to the deficiency of an enzyme, aspartoacylase. This enzyme deficiency leads to increased excretion in the urine of a substance called N-acetylaspartic acid (NAA).

The diagnosis of Canavan disease can be made by finding an increased level of NAA in the urine. The abnormally high levels of NAA lead to a loss of insulation (demyelination) and spongy degeneration of the brain. An alternative name for Canavan disease is spongy degeneration of the central nervous system.