Tyrosinemia type I, also known as hepatorenal tyrosinemia, is a rare inborn error of tyrosine metabolism. Clinical symptoms are highly variable even among members of the same family and affected individuals can present at any time from the neonatal period to adulthood. The disorder has been classified based on the age of onset, which broadly correlates with disease severity. The acute form typically presents prior to 6 months of age with acute liver failure. A sub-acute form manifests between 6 months and 1 year of age with liver disease, hypoglycemia, failure to thrive, coagulopathy, hepatosplenomegaly, renal Fanconi syndrome that may lead to rickets, and hypotonia. The chronic form presents after the first year of life with chronic liver disease, renal disease, rickets, cardiomyopathy and/or neurologic crises similar to porphyria. Patients with all forms have a high risk of developing hepatocarcinoma, even at a very young age.