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Tyrosinemia

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Tyrosinemia
ICD-10 E702
ICD-9 270.2
OMIM 276700 276600 276710
DiseasesDB 13478 13486 29836
MedlinePlus [1]
eMedicine ped/2339
MeSH {{{MeshNumber}}}

Tyrosinemia (or "Tyrosinaemia") is an error of metabolism, usually inborn, in which the body can not effectively break down the amino acid tyrosine.

Tyrosinemia is inherited in an autosomal recessive pattern. There are three types of tyrosinemia, each with distinctive symptoms and caused by the deficiency of a different enzyme.

TypesEdit

Autorecessive

Tyrosinemia is inherited in an autosomal recessive pattern.

Type I tyrosinemiaEdit

Type I tyrosinemia (OMIM 276700) is the most severe form of this disorder and is caused by a shortage of the enzyme fumarylacetoacetate hydrolase (EC 3.7.1.2), encoded by the gene FAH found on chromosome number 15. Fumarylacetoacetate hydrolase is the last in a series of five enzymes needed to break down tyrosine. Symptoms of type I tyrosinemia usually appear in the first few months of life and include failure to gain weight and grow at the expected rate (failure to thrive), diarrhea, vomiting, yellowing of the skin and whites of the eyes (jaundice), cabbagelike odor, and increased tendency to bleed (particularly nosebleeds). Type I tyrosinemia can lead to liver and kidney failure, problems affecting the nervous system, and an increased risk of liver cancer.

Worldwide, type I tyrosinemia affects about 1 person in 100,000. This type of tyrosinemia is much more common in Quebec, Canada. The overall incidence in Quebec is about 1 in 16,000 individuals. In the Saguenay-Lac-Saint-Jean region of Quebec, type 1 tyrosinemia affects 1 person in 1,846.

Type II tyrosinemiaEdit

Type II tyrosinemia (OMIM 276600) is caused by a deficiency of the enzyme tyrosine aminotransferase (EC 2.6.1.5), encoded by the gene TAT. Tyrosine aminotransferase is the first in a series of five enzymes that converts tyrosine to smaller molecules, which are excreted by the kidneys or used in reactions that produce energy. This form of the disorder can affect the eyes, skin, and mental development. Symptoms often begin in early childhood and include excessive tearing, abnormal sensitivity to light (photophobia), eye pain and redness, and painful skin lesions on the palms and soles. About half of individuals with type II tyrosinemia are also mentally retarded. Type II tyrosinemia occurs in fewer than 1 in 250,000 individuals.

Type III tyrosinemiaEdit

Type III tyrosinemia (OMIM 276710) is a rare disorder caused by a deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27), encoded by the gene HPD. This enzyme is abundant in the liver, and smaller amounts are found in the kidneys. It is one of a series of enzymes needed to break down tyrosine. Specifically, 4-hydroxyphenylpyruvate dioxygenase converts a tyrosine byproduct called 4-hydroxyphenylpyruvate to homogentisic acid. Characteristic features of type III tyrosinemia include mild mental retardation, seizures, and periodic loss of balance and coordination (intermittent ataxia). Type III tyrosinemia is very rare; only a few cases have been reported.

TreatmentEdit

Treatment varies depending on the specific type. A low protein diet may be required in the management of tyrosinemia. Recent experience with NTBC has shown to be very effective.

See alsoEdit

External linksEdit

ReferencesEdit

  1. Charles Scriver, Beaudet, A.L., Valle, D., Sly, W.S., Vogelstein, B., Childs, B., Kinzler, K.W. (Accessed 2007). The Online Metabolic and Molecular Bases of Inherited Disease. New York: McGraw-Hill. - Summaries of 255 chapters, full text through many universities. There is also the OMMBID blog.

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