Hereditary tyrosinemia type 1

Hereditary tyrosinemia type 1 is one of the most common recessive genetic disorders in some regions of Québec:

• Saguenay–Lac-Saint-Jean
• Charlevoix
• Haute-Côte-Nord

Hereditary tyrosinemia type 1 is a liver disease caused by an enzyme deficiency, in this case the enzyme fumarylacetoacetate hydrolase (FAH). This enzyme is necessary to break down tyrosine, an amino acid present in several animal and plant proteins contained in food. For example, meat, dairy products, fish, eggs, legumes, nuts and tofu contain tyrosine.

Because of FAH deficiency, metabolic waste cannot be broken down. It then accumulates in the body, damaging the liver, kidneys and central nervous system (nerves).

Appropriate treatment can reduce the build-up of metabolic waste products and thus improve the life expectancy and quality of life of people who have the disease.

A child with untreated hereditary tyrosinemia type 1 generally presents with the following symptoms:

• failure to thrive (poor growth)
• vomiting
• bleeding (such as nose bleeds)
• in some children: irritability, pains in the limbs in the first few months of life
• progressive deterioration of the kidneys and especially the liver.

Treatment of hereditary tyrosinemia type 1 combines two elements: a diet low in tyrosine and a drug, nitisinone (also known as NTBC).

• Nitisinone is a drug that acts on the digestion of tyrosine, thus preventing the build-up of waste products that damage the liver, kidneys and nerves.

Nitisinone therapy and dietary changes may slow the progression of the disease, but will not cure it.

At this time, children treated with nitisinone develop normally. However, the drug can have side effects that may cause complications in the long term. For example, if a child's health deteriorates despite treatment, they may be given a liver transplant. The transplant can cure the disease. The child no longer needs to follow a diet, but must take medication for the rest of their life to ensure the success of the transplant in the long term.

Affected children are followed by specialized teams of professionals from the health and social services network.

Hereditary tyrosinemia type 1 is a recessive genetic disorder.

To find out more, go to the page About autosomal recessive hereditary diseases.

It is impossible to prevent Hereditary tyrosinemia type 1 in newborns who have received a copy of the variant in a gene from each of their biological parents. However, the variant responsible for the disease can be detected in a simple, rapid and inexpensive way.

The Ministère de la Santé et des Services sociaux (MSSS) and the Centre intégré universitaire de santé et de services sociaux (CIUSSS) du Saguenay–Lac-Saint-Jean offer screening tests to identify carriers of this disease.

To find out more, go to the page Carrier screening for autosomal recessive hereditary diseases in people from the Saguenay–Lac-Saint-Jean, Charlevoix and Haute-Côte-Nord regions.

Neonatal screening

Hereditary tyrosinemia type 1 is one of the diseases that all newborns in Quebec are screened for a few hours after birth. Screening is provided under the MSSS’s Québec Neonatal Screening Program. Thanks to screening, an affected child can start treatment quickly and maintain a good quality of life. Early treatment also allows their family to cope better with the disease.

For help or more information on hereditary tyrosinemia type 1, please visit the following links:

• Groupe d’aide aux enfants tyrosinémiques du Québec (in French only)
• Corporation de recherche et d’action sur les maladies héréditaires (in French only)