July 3, 2008

Tyrosinaemia

By Sarah H

This is part four in the series for Metabolic Disease Awareness Week. It focuses on Tyrosinaemia which is another inborn error of metabolism (metabolic disease) caused by a deficiency in fumaryl-acetoacetate hydrolase.

There are 3 types of this disorder:

 • Tyrosinaemia Type I
 • Tyrosinaemia Type II  (Richner-Hanhart syndrome)
 • Tyrosinaemia Type III.

Tyrosinaemia Type I is caused by a shortage of the enzyme: fumarylacetoacetate hydrolase. It has an incidence of approximately 1:100,000. The symptoms will appear in the first few months of life. These include:

 • Failure to trive.
 • Lethargy.
 • Diarrhoea.
 • Jaundice.
 • Bleeding.
 • Liver failure.
 • Kidney failure.

Treatment is nutritional based, with a diet  requiring a low phenylalanine and tyrosine: this generally means a low protein diet, with no fish, meat eggs or nuts. There is also the drug Nitisinone (NTBC) available.

Tyrosinaemia Type II is caused by a shortage of the enzyme: tyrosine aminotransferase. It has an incidence of approximately 1:250,000. The symptoms will appear in early childhood. These include:

 • Corneal erosions and ulcers (resulting in sensitivity to light and pain to the eyes).
 • Poor mental development.
 • Palm and sole erosions.

Treatment again is nutritional based, and is similar to type I with a diet  requiring a low phenylalanine and tyrosine.

Tyrosinaemia Type III  is caused by a shortage of the enzyme: 4-hydroxyphenylpyruvate dioxygenase. It is very rare.  The symptoms will appear in early childhood. These include:

 • Seizures.
 • Poor mental development.
 • Loss of balance and coordination

It is another disorder that is inherited in a autosomal recessive manner. This means that the parents of the affected child carry a genetic trait that cause Tyrosinamemia.

Topics: Thoughts on Tyrosinaemia |

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