Tyrosinemia type 3 is an inborn error of tyrosine metabolism characterised by mild hypertyrosinemia and increased urinary excretion of 4-hydroxyphenylpyruvate, 4-hydroxyphenyllactate and 4-hydroxyphenylacetate.Last update: November 2010
It is the least frequent form of tyrosinemia (see this term) with less than 20 cases reported in the literature so far.
The clinical picture is highly variable ranging from asymptomatic in patients identified through neonatal screening program studies to patients with neurologic manifestations including intellectual deficit and ataxia.
Tyrosinemia type 3 is caused by mutations in the HPD gene (12q14-qter) encoding 4-hydroxyphenylpyruvate dioxygenase.
Tyrosinemia type 3 is transmitted as an autosomal recessive trait
Despite the variable clinical picture, patients with tyrosinemia type 3 are recommended to follow a phenylalanine- and tyrosine-restricted diet.