Tyrosine is an amino acid, one of numerous building blocks that are needed to make proteins. Numerous inherited human diseases are the result of gene mutations that in some way impact the metabolism of amino acids.
This rare disorder results from a deficiency in a liver enzyme needed to convert tyrosine into a useable form. The result is an accumulation of this amino acid in the blood and cells. This may lead to growth and mental retardation. Developmental milestones such as sitting and walking are often delayed. Elevated, painful lesions on the palms and soles are often present. The surface of the cornea (windshield of the eye) may become inflamed and irregular causing, pain, redness, sensitivity to light, and excessive tearing. Sometimes the cornea becomes ulcerated and scarred thereby interfering with vision.
This is an autosomal recessive condition requiring the presence of two mutations. The parents, who are clinically normal, may each contribute a single mutation to their child who now has the double dose necessary for the disease to appear. The risk for tyrosinemia II in each of their children is 25%.
The diagnosis may be made by a pediatrician through urine and blood tests. A diet low in protein may decrease the corneal and skin lesions but its impact on the growth and mental deficits is unknown at this time.