Tyrosinemia

The tyrosinemias are characterized by the accumulation of tyrosine in body fluids and tissues. Type I is the most severe form of tyrosinemia, is caused by a deficiency of fumarylacetoacetate hydrolase (FAH). This disorder is associated with liver failure, painful neurologic crises, rickets, and hepatocarcinoma. Type II is caused by a deficiency of tyrosine aminotransferase (TAT), and clinically presents with hyperkeratotic plaques on the hands and soles of the feet and photophobia due to deposition of tyrosine crystals within the cornea. Type III is a rare disorder caused by a deficiency of 4-hydroxyphenylpyruvate dioxygenase, that is associated with ataxia and mild mental retardation.