Canavan disease (patient information)
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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 ten different chemicals. Each of the leukodystrophies affects one (and only one) of these substances.
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)
- An abnormally large, poorly controlled head
- Hearing loss
- Backflow of food material into the nose (nasal regurgitation)
- Swallowing difficulities
Children are characteristically quiet and apathetic.
Who is at highest risk?
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%) chance with each pregnancy that the child will be affected with Canavan disease.
When to seek urgent medical care?
The gene for Canavan disease has been located. Many laboratories offer prenatal screening for this disorder to populations at risk.
Your doctor may conduct a physical examination to look for signs such as:
- Exaggerated reflexes (hyperreflexia)
- Joint stiffness
- Loss of tissue in the optic nerve of the eye (optic atrophy)
Your doctor may also conduct tests such as:
- Blood chemistry
- CSF chemistry
- Genetic testing for aspartoacylase gene mutations
- Head CT scan
- Head MRI scan
- Urine chemistry
Canavan disease causes progressive brain atrophy, meaning the permanent loss of functional brain tissue. There is no cure, nor is there a standard course of treatment. Treatment is symptomatic and supportive. As a parent, please talk with your health care provider about emotional counseling and support groups in your area. Social workers may be available to assist you and your family through your child's course of Canavan disease.
What to expect (Outlook/Prognosis)?
With Canavan disease, the central nervous system breaks down. Patients are likely to become disabled. Overall prognosis is poor. Death often occurs before 18 months of age. Most patients die before the age of 4. However, some patients live until they are teenagers or, rarely, young adults.
This is often a fatal disorder. It includes severe disabilities such as:
- Inability to walk
- Mental retardation
Genetic counseling is recommended for people who want to have children and have a family history of Canavan disease. Counseling should be considered if both parents are of Ashkenazi Jewish descent. For this group, DNA testing can almost always tell whether one or both parents is a carrier.
A diagnosis may be made before the baby is born (prenatal diagnosis) by testing the amniotic fluid.