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Tyrosinemia

Tyrosinemia Overview

In tyrosinemia, the body doesn't have an enzyme it needs [called fumarylacetoacetate hydrolase (FAH)] to metabolize tyrosine. Metabolism is a process in which our bodies break down substances as we use them for energy; in this case tyrosine. Tyrosine is an amino acid that is found in most proteins. People with tyrosinemia can't break down proteins, so the proteins build up in their bodies and become toxic. This causes progressive damage to the liver and kidneys, but mainly the liver. This is because the liver is normally the primary place tyrosine is metabolized.

Tyrosinemia is hereditary; in order to have the disease, a child must carry one gene for tyrosinemia from each parent. In families where both parents carry the gene, there is a one in four risk that a child will have tyrosinemia. There is now a genetic test available, so that couples at high risk of being carriers can determine their risk of having a child with tyrosinemia. This is a very rare disease; only about one person in 100,000 has it.

Tyrosinemia Symptoms

Symptoms of tyrosinemia tend to fall into two categories, acute and chronic.

In the acute form of tyrosinemia, babies experience symptoms within a month of birth. They may not gain weight properly, have an enlarged liver and spleen and a swollen abdomen, which are symptoms of other liver diseases. Jaundice may or may not be prominent. Babies with tyrosinemia also have swelling of the legs, and an increased tendency to bleed, particularly nosebleeds. These babies need liver transplants right away.

Other children have a form of tyrosinemia with a more gradual onset and less severe symptoms. Enlargement of the liver and spleen are the main symptoms, the abdomen is distended with fluid, and these children also sometimes have trouble gaining weight. They may vomit or have diarrhea. Liver disease develops more slowly, eventually leading to cirrhosis. These children will also need liver transplants, but not as quickly. Some kids can be treated for years, if necessary, before receiving a transplant.

Tyrosinemia Diagnosis

Tyrosinemia is diagnosed based on blood tests and urine tests. In both the acute and chronic forms of the disease, liver function tests are often abnormal. Low serum albumin and clotting factors are also frequently found. Because of the biochemical defect, abnormal products may be measured in the urine which confirm the diagnosis.

It is possible to test for tyrosinemia while the baby is still developing in the womb. Doctors can measure succinylacetone or FAH levels in the amniotic fluid. If there is too much FAH, it may mean that the fetus is not able to break it down.

Tyrosinemia Treatment

For children with the chronic form of tyrosinemia, the first line of defense is usually a low-protein diet. Meats, dairy products, and other protein rich foods such as nuts and beans should be avoided. Good nutrition and adequate vitamin and mineral intake do not cure tyrosinemia, but help children grow normally and minimize the protein build-up.

Liver transplantation is still the only way to correct the metabolism of tyrosine. At present, every child with tyrosinemia needs a new liver sooner or later, depending on the stage of the disease. However, after receiving a transplant, many of them can go on to lead healthy, active lives.

Learn about other Liver Disease States.

Last Update
November 18, 2010

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