Tyrosinemia Treatment and Symptoms

What Is Tyrosinemia?

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. When people with tyrosinemia break down protein, abnormal toxic break down products of tyrosine build up in their bodies. 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 get a mutation in the gene for tyrosinemia from each parent. In families where both parents carry a mutation, 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 in Children

Tyrosinemia symptoms tend to fall into two categories, acute and chronic.

In the acute form of tyrosinemia, babies experience symptoms within months 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 is unusual. Babies with tyrosinemia also have swelling of the legs, and an increased tendency to bleed, particularly nosebleeds. These babies may need liver transplants right away.

The chronic form of tyrosinemia presents after 6 months 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 may have trouble gaining weight. They may vomit or have diarrhea. Liver disease develops more slowly, eventually leading to cirrhosis.

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, the abnormal product Succinylacetone may be measured in the urine, which confirms the diagnosis.

In the United States tyrosinemia is included in the newborn screening programme, so nowadays children are usually detected before they become unwell.

It is possible to test for tyrosinemia while the baby is still developing in the womb. Doctors can detect mutations or measure succinylacetone in the amniotic fluid.

Tyrosinemia Treatment

The treatment for tyrosinemia is a combination of a low-protein diet and a drug called Nitisinone. Nitisinone prevents the build up of toxic breakdown products. Meats, dairy products, and other protein rich foods such as nuts and beans should be avoided. Good nutrition and adequate vitamin and mineral intake allow children to grow normally. Children with tyrosinemia do require careful monitoring to ensure normal growth and because there is a risk of developing liver cancer. Children who are treated following newborn screening do not seem to develop liver disease in childhood. For unknown reasons some children with tyrosinemia have learning difficulties.

Liver transplantation is still the only way to correct the metabolism of tyrosine, but this is rarely necessary nowadays. More than 90% of children respond very well to Nitisinone and diet. At present, liver transplantation is only needed where children with the acute form do not respond to Nitisinone rapidly or where liver cancer is suspected. After receiving a transplant, children can eat a normal diet and lead healthy, active lives.

Learn about other Liver Disease States.