Canavan disease

Definition

Canavan disease is an inherited condition that affects the breakdown and use (metabolism) of aspartic acid.

Alternative Names

Spongy degeneration of the brain; Aspartoacylase deficiency

Causes, incidence, and risk factors

Canavan disease is passed down (inherited) through families. It is more common among Ashkenazi Jews than in the general population.

The lack of the enzyme, aspartoacylase, leads to a buildup of material called N-acetylaspartic acid in the brain. This causes the white matter of the brain to break down (deteriorate).

Symptoms

Symptoms usually begin in the first year of life. Parents tend to notice when a child is not reaching certain developmental milestones, including head control.

Symptoms include:

• Abnormal posture with flexed arms and straight legs
• Backflow of food material into the nose (nasal regurgitation)
• Feeding problems
• Increasing head size (macrocephaly)
• Irritability
• Lack of head control when baby is pulled from a lying to a sitting position (head lag)
• Poor muscle tone, especially of the neck muscles
• Poor visual tracking or blindness
• Reflux with vomiting
• Seizures
• Severe mental retardation
• Swallowing difficulties

Signs and tests

• Exaggerated reflexes (hyperreflexia)
• Joint stiffness
• Loss of tissue in the optic nerve of the eye (optic atrophy)

Tests:

• Blood chemistry
• CSF chemistry
• Genetic testing for aspartoacylase gene mutations
• Head CT scan
• Head MRI scan
• Urine chemistry

Treatment

Treatment mostly aims to ease the symptoms of the disease. Lithium and other drugs are being investigated.

Support Groups

Additional information and resources are available from:

• Canavan Foundation: www.canavanfoundation.org
• Jacob's Cure: www.jacobscure.org

Expectations (prognosis)

With Canavan disease, the central nervous system breaks down. Patients are likely to become disabled.

Death often occurs before 18 months of age. However, some patients live until they are teenagers or, rarely, young adults.

Complications

This is often a fatal disorder. It includes severe disabilities such as:

• Blindness
• Inability to walk
• Mental retardation

Calling your health care provider

Call your health care provider if your child has any symptoms of Canavan disease.

Prevention

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.

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References

Rezvani I. Defects in metabolism of amino acids. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 85.