Tyrosinemia type I is an autosomal recessive disorder caused by a deficiency of the enzyme fumarylacetoacetate hydrolase (FAH). The disease manifests primarily as liver disease, with hepatic cirrhosis and accompanying renal tubule damage as a result of the build up of succinylacetone. Biochemically, the hallmarks of the disease are elevated blood tyrosine and methionine, elevated blood alpha-fetoprotein, and succinylacetone in the urine. The diagnosis is confirmed by the presence of succinylacetone in urine. Tyrosinemia type I is treated by a low-tyrosine diet and the medication Orfadin (nitisinone). Nitisinone blocks the tyrosine breakdown pathway prior to the FAH deficiency and prevents the formation of succinylacetone.