CANAVAN DISEASE

What Is Canavan Disease?

Canavan disease, one of the most common cerebral degenerative diseases of infancy, is a gene-linked, neurological birth disorder in which the white matter of the brain degenerates into spongy tissue riddled with microscopic fluid-filled spaces. Canavan disease is one of a group of genetic disorders known as the leukodystrophies. These diseases cause imperfect growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fibers in the brain. Myelin, which lends its color to the "white matter" of the brain, is a complex substance made up of at least 10 different chemicals. Each of the leukodystrophies affects one (and only one) of these substances.

Canavan disease is caused by mutations in the gene for an enzyme called aspartoacylase. Symptoms of Canavan disease, which appear in early infancy and progress rapidly, may include mental retardation, loss of previously acquired motor skills, feeding difficulties, abnormal muscle tone (floppiness or stiffness), and an abnormally large, poorly controlled head. Paralysis, blindness or hearing loss also may occur. Children are characteristically quiet and apathetic. Although Canavan disease may occur in any ethnic group, it is more frequent among Ashkenazi Jews from eastern Poland, Lithuania and western Russia, and among Saudi Arabians. Canavan disease can be identified by a simple prenatal blood test that screens for the missing enzyme or for mutations in the gene that controls aspartoacylase. Both parents must be carriers of the defective gene in order to have an affected child. When both parents are found to carry the Canavan gene mutation, there is a one in four (25 percent) chance with each pregnancy that the child will be affected with Canavan disease.

Is There Any Treatment?

Canavan disease causes progressive brain atrophy. There is no cure, nor is there a standard course of treatment. Treatment is symptomatic and supportive.

What Is the Prognosis?

The prognosis for Canavan disease is poor. Death usually occurs before age 4, although some children may survive into their teens and 20s.

What Research Is Being Done?

The gene for Canavan disease has been located. Research supported by the National Institute of Neurological Disorders and Stroke, a part of the National Institutes of Health, includes studies to understand how the brain and nervous system normally develop and function and how they are affected by genetic mutations. These studies contribute to a greater understanding of gene-linked disorders such as Canavan disease and have the potential to open promising new avenues of treatment.