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Parents and caregivers focus on making the child as comfortable as possible. If you care for your child at home, your doctor and other trained health care specialists will help you learn how to meet your child’s needs. If you cannot care for your child at home, an extended care center that has experience caring for children with Tay-Sachs disease is an option. You and your other children may benefit from talking with a mental health professional, who can help you cope with the emotional difficulties of having a child or sibling with a fatal disease.

Canavan Disease

Canavan disease is a rare, inherited brain disorder resulting from an enzyme deficiency that causes a normal substance called N-acetylaspartic acid to build up in the brain in much higher-than-normal amounts. The excess N-acetylaspartic acid destroys the protective covering (myelin sheath) around brain cells. As the myelin sheath degenerates, the white matter of the brain becomes spongy and develops spaces filled with fluid. N-acetylaspartic acid also builds up in the urine (where it does not pose any health risks).

The gene that transmits Canavan disease is recessive, which means that a child must inherit two copies of the defective gene (one from each parent) to have the disease. The disorder affects primarily people of Eastern European, Jewish (Ashkenazi) descent. For this reason, Ashkenazi Jewish couples are offered genetic testing before they start planning a family to determine if they are carriers of the gene. If you and your partner are carriers of the gene, a genetic counselor can help you evaluate your risk of having a child with the disorder and explain various family planning options you might want to consider.

Symptoms

Signs and symptoms of Canavan disease appear in early infancy and include a rapidly enlarging head circumference, loss of acquired motor skills, feeding problems, floppy or stiff muscle tone, and poor head control. Children with the disorder cannot crawl, walk, sit up, or speak. Over time, they may become mentally retarded, have seizures, and become blind. The symptoms vary from child to child and may progress in different ways, but most affected children do not live beyond age 10.

Inborn Errors of Metabolism

Inborn errors of metabolism are genetic disorders that disturb the body’s biochemical processes. Most inborn errors of metabolism are autosomal recessive disorders. The genetic defect can either produce a deficiency of a particular enzyme that controls a specific chemical reaction inside the body or prevent a particular enzyme from working properly. Many inborn errors of metabolism can be treated with a restricted diet, supplements of the deficient enzyme, or a medication that makes the enzyme work more effectively. The severity of these disorders can range from mild to severe. All states require testing of all newborns for some inborn errors of metabolism, including phenylketonuria, or PKU (see next page), shortly after birth. Additional newborn screening tests for more than 40 different inborn errors of metabolism, which are available through commercial laboratories, are gradually being added to state programs.

Diagnosis and Treatment

To diagnose Canavan disease in a child, doctors use a urine test that measures the amount of N-acetylaspartic acid in the child’s urine. Before birth, prenatal diagnostic tests such as chorionic villus sampling, or CVS (see page 511), or amniocentesis (see page 510) can determine if the fetus has Canavan disease. At-risk people who are planning a family can have a blood test to detect the defective gene.

WARNING!

In an Emergency: Inborn Errors of Metabolism

A person who has an inborn error of metabolism can become seriously ill very quickly. In extreme cases, he or she can lapse into a coma and die. If your child has an inborn error of metabolism and is in a crisis, act quickly by doing the following:

• Don’t give your child anything to eat or drink.

• Call the doctor and take your child to a hospital emergency department immediately.

• Tell emergency department