Type I tyrosinemia

Type I tyrosinemia is a rare autosomal recessive metabolic disorder that is characterized by a deficiency of the enzyme fumarylacetoacetate hydrolase (FAH), which is necessary for the final step in the breakdown of the amino acid tyrosine. This deficiency results in an accumulation of toxic substances in the blood and tissues, which can lead to severe liver and kidney damage.

Symptoms

The symptoms of Type I tyrosinemia typically become apparent in the first few months of life and may 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), a cabbage-like odor, and increased tendency to bleed (particularly nosebleeds).

Causes

Type I tyrosinemia is caused by mutations in the FAH gene. These mutations lead to a deficiency of the enzyme FAH, which is necessary for the final step in the breakdown of tyrosine. Without enough FAH, tyrosine and its byproducts build up in tissues and organs, which can lead to the signs and symptoms of this disorder.

Diagnosis

Diagnosis of Type I tyrosinemia is based on the symptoms, laboratory testing showing elevated tyrosine levels in the blood, and genetic testing confirming a mutation in the FAH gene.

Treatment

Treatment for Type I tyrosinemia typically involves a medication called nitisinone and a low-protein diet. Nitisinone works by preventing the buildup of tyrosine and its byproducts. A low-protein diet helps to limit the amount of tyrosine in the body.

Prognosis

With early diagnosis and treatment, individuals with Type I tyrosinemia can often live healthy lives. However, without treatment, this disorder can lead to liver and kidney failure, and in some cases, can be life-threatening.

See also

• Tyrosinemia
• Metabolic disorder
• FAH gene

Type I tyrosinemia Resources
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