Tyrosinemia, Type I (TYR I)



Tyrosinemia, type I (TYR I) is an inherited condition in which the body is unable to break down certain building blocks of proteins, known as amino acids. Individuals with this condition are unable to break down the amino acid tyrosine. Early detection and treatment can often prevent many of the serious outcomes of TYR I. There are three types of tyrosinemia — I, II, and III. Type I is the most severe of the three forms. Signs of TYR I usually begin in the first few months of life, though some individuals do not begin showing signs until childhood. Signs of TYR I include diarrhea, bloody stool, vomiting, poor weight gain, sleeping longer and more often, tiredness, irritability, “cabbage-like” odor, yellowing skin (jaundice), increased bleeding or bruising, swollen legs or abdomen, developmental delays, and trouble breathing. Many of these signs may occur when a baby eats foods the body cannot break down.

Condition Type:

Core Conditions


Tyrosinemia, type I (TYR I) affects about 1 in 100,000 individuals worldwide.

More Information for Parents:
Also known as:
  • TYR I
  • Hypertyrosinemia
  • Hereditary tyrosinemia
  • Hepatorenal tyrosinemia
  • Fumarylacetoacetase deficiency
  • Fumarylacetoacetate hydrolase deficiency
  • FAH deficiency
  • Tyrosinosis

Core Conditions