Tyrosinemia type II (TYRII) is an amino acid disorder that causes the body to have reduced production of an enzyme called hepatic tyrosine aminotransferase. Without this enzyme a protein called tyrosine builds up in the body and can cause symptoms such as pain and redness in the eye, painful skin thickening of the palms of the hand and soles of the feet, and intellectual disability. Not everyone diagnosed with TYRII will have the same symptoms and some may have more severe symptoms than others. While there are not many reported cases, available reports indicate that if a pregnant mother with TYRII is not treated it can cause growth problems or developmental delay in the unborn baby.
TYRII is reported to be rare, affecting less than 1/250,000 individuals. It has been reported in individuals of Italian, Ashkenazi Jewish, French, Scottish, Northern European, Japanese, and Middle Eastern ancestry. The diagnosis may be most common in individuals of Arab or Mediterranean ancestry, based on documented case reports.
A low protein diet and restricting food sources of tyrosine and phenylalanine (such as artificial sweeteners) can improve symptoms associated with TYRII for some affected individuals. Beginning treatment early in life appears to reduce the severity of mental impairment, as well as the eye and skin symptoms for some individuals. There are special supplements and foods for babies and adults with TYRII. Additional medications such as oral retinoids may be useful in the treatment of the skin abnormalities.
The symptoms of an individual affected with TYRII tend to progress and persist unless the dietary restrictions are implemented. Many affected individuals see improvement in the eye and skin symptoms after removing tyrosine and phenylalanine from the diet. Infants who are diagnosed with TYRII very early and who start treatment right away can usually have a healthy and normal life. About half of individuals with TYRII have some sort of intellectual disability, but early treatment may reduce this risk.
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Explanations of an extensive number of genetic diseases written for everyday people by the U.S. government's National Institutes of Health.
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