Q. What is Tyrosinemia?

There are two forms of hereditary tyrosinemia. They are tyrosinemia Type I and tyrosinemia Type II. Type I was thought to be due to a deficiency of parahydroxy phenylpyruvic acid oxidase. But recently secondary impairment in this enzyme has been attributed to a primary defect of hepatic firnaryl acetoacetate hydrolase. Patients with deficiency show renal tubular impairment, hypophosphatemic rickets, liver failure and hypertension. The plasma concentrations of phenylalanine and tyrosine are elevated.

In tyrosinemia type 11, there is a very elevated concentration of blood and urine tyrosine. Increase in urinary phenolic acids, N-acetyltyrosine and tyramine is seen.

Other symptoms include corneal erosions, hyperkeratosis on the fingers and palms and sole of the feet. Mental retardation may occur.