Canavan Disease: Causes and Characteristics
Canavan disease (also known as Canavan-Van Bogaert-Bertrand disease), a relatively common cerebral degenerative disease, was first described by U.S. physician Myrtelle May Canavan in 1931. While it can affect individuals belonging to any ethnic group, it most often afflicts Jewish people of Ashkenazi (e.g., Eastern European) descent, as well as Saudi Arabian people, albeit to a lesser extent. The incidence of carriers among Ashkenazi Jews is approximately 1 in 40. Canavan disease is included in a group of genetic disorders referred to as leukodystrophies; these disorders cause impaired development of the myelin sheath, which functions as an “insulator” surrounding the nerve fibers in the brain. This leads to progressive brain atrophy.
Pathophysiology of Canavan Disease
Researchers have located the gene that causes Canavan disease, a defective ASPA gene responsible for producing the enzyme aspartoacylase. The function of aspartoacylase is to break down N-acetyl aspartate, a concentrated brain molecule. The defective ASPA gene cannot produce sufficient amounts of aspartoacylase, which then leads to an inability to break down N-acetyl aspartate. Researchers believe this diminished breakdown activity prevents myelin sheath growth, which in turn hinders the normal transmission of nerve impulses.
Infants afflicted with Canavan disease exhibit symptoms shortly after birth, and these symptoms develop very quickly. Characteristics of the disease include: abnormal muscle tone in the form of stiffness or floppiness, loss of gross and fine motor skills, an inability to feed, an unusually large head and concurrent poor head control, mental retardation, hearing loss, apathy, blindness, seizures, and paralysis. There is no cure for this disease, nor is there a standard treatment protocol, and most children afflicted with Canavan disease die by the age of four. However, some afflicted individuals have managed to live into their teens or twenties, although this is rare.
Although a cure has not yet been developed, researchers have made considerable progress in developing treatments for the disease. For example, researchers at Cooper University Hospital in New York have developed a form of brain gene therapy involving the insertion of six catheters into the brain that deliver a solution containing 600 to 900 billion virus particles of an aspartoacylase substitute.
This post is part of the series: The Ashkenazi Jewish Genetics Panel
This series describes the diseases tested for in the Ashkenazi Jewish Genetics Panel (AJGP).