Tyrosinemia type I is a disorder that affects how the body breaks down an amino acid called tyrosine, which is important for building proteins. In this condition, the body lacks an enzyme called fumarylacetoacetate hydrolase, leading to a buildup of tyrosine and related substances. This accumulation can harm tissues and organs.
Symptoms usually start in the first few months of life and can include diarrhea, vomiting, an enlarged liver, slow growth, yellowing of the skin and eyes (jaundice), weakened bones, irritability, and a peculiar odor resembling boiled cabbage or rotten mushrooms. Tyrosine buildup can also affect the cornea, causing itchy and irritated eyes. The liver, kidneys, and central nervous system are progressively damaged. Without treatment, children may experience episodes of abdominal pain, changes in mental state, pain or numbness in extremities, and respiratory failure, requiring a mechanical ventilator. The drug nitisinone, approved by the FDA in 2002, is used to treat tyrosinemia type I. It prevents the accumulation of specific substances in individuals with the disease and is taken as soon as the condition is diagnosed. Early recognition and treatment are crucial for a better prognosis and less damage to the body.
Tyrosinemia type I is caused by pathogenic (disease-causing) variants in the FAH gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 143 chance to be a carrier.
Other names for this condition are hereditary tyrosinemia, hypertyrosinemia, and tyrosinaemia.