Type I tyrosinemia is a rare and inherited metabolic disorder characterized by the body's inability to efficiently break down the amino acid tyrosine. It is caused by a deficiency of the enzyme fumarylacetoacetate hydrolase (FAH), which is necessary for the final step in the breakdown of tyrosine. Without this enzyme, toxic byproducts build up in the body, leading to various health problems.
Individuals with type I tyrosinemia typically exhibit symptoms early in infancy. These symptoms include failure to thrive, poor weight gain, developmental delays, and an enlarged liver and spleen. Additionally, affected individuals may experience cabbage-like odor of the sweat, respiratory problems, kidney problems, and yellowing of the skin and eyes (jaundice). If left untreated, type I tyrosinemia can lead to liver failure, kidney dysfunction, and potentially life-threatening complications.
The diagnosis of type I tyrosinemia is typically made through blood and urine tests that measure the levels of tyrosine and its byproducts. Genetic testing can also be conducted to confirm the presence of mutations in the FAH gene.
The standard treatment for type I tyrosinemia is a restrictive diet that limits the intake of tyrosine and phenylalanine, another amino acid. This diet aims to reduce the accumulation of toxic byproducts in the body. In some cases, medication such as nitisinone may also be prescribed to inhibit the production of toxic metabolites. Liver transplantation may be considered in severe cases where the disease progresses despite dietary and medical interventions.
With early diagnosis and consistent management, individuals with type I tyrosinemia can lead relatively normal lives, although close monitoring and lifelong dietary restrictions are often necessary.
