Canavan disease

Canavan disease is a gene-linked neurological disorder in which the brain degenerates into spongy tissue riddled with microscopic fluid-filled spaces.

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Canavan disease infographic

Leukodystrophy

Canavan disease has been classified as one of a group of genetic disorders known as the leukodystrophies.

Pathophysiology

Recent research has indicated that the cells in the brain responsible for making myelin sheaths, known as oligodendrocytes, cannot properly complete this critical developmental task.  Myelin sheaths are the fatty covering that act as insulators around nerve fibers in the brain, as well as providing nutritional support for nerve cells.  In Canavan disease, many oligodendrocytes do not mature  and instead die, leaving nerve cell projections known as axons vulnerable and unable to properly function.  

Cause

Canavan disease is caused by mutation in the gene for an enzyme called aspartoacylase, which acts to break down the concentrated brain chemical known as N-acetyl-aspartate.

Symptoms

Symptoms of Canavan disease usually appear in the first 3 to 6 months of life and progress rapidly.  Symptoms include lack of motor development, feeding difficulties, abnormal muscle tone (weakness or stiffness), and an abnormally large, poorly controlled head. Paralysis, blindness, or hearing loss may also occur. Children are characteristically quiet and apathetic.

Genetics

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.

Diagnosis

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.

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Demyelinating disorder

Inheritance

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.

Prognosis

The prognosis for Canavan disease is poor. Death usually occurs before age 10, although some children may survive into their teens and twenties.

Treatment

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