<unk>  is a rare disorder caused by a deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27), encoded by the gene HPD. This enzyme is abundant in the liver, and smaller amounts are found in the kidneys. It is one of a series of enzymes needed to break down tyrosine. Specifically, 4-hydroxyphenylpyruvate dioxygenase converts a tyrosine byproduct called 4-hydroxyphenylpyruvate to homogentisic acid. Characteristic features of<unk>  include mild mental retardation, seizures, and periodic loss of balance and coordination (intermittent ataxia).<unk>  is very rare; only a few cases have been reported.
Type III tyrosinemia
Type II tyrosinemia
Type I tyrosinemia
Tyrosinemia
Essential fructosuria
Phenylketonuria
Familial hyperchylomicronemia
Glycogen storage disease type I CT