Tyrosinemia Type I
Description
Tyrosinemia Type I, also known as hereditary tyrosinemia, is a rare genetic disorder that primarily affects the liver and kidneys. It‘s caused by a deficiency in the enzyme fumarylacetoacetase (FAH), crucial for breaking down the amino acid tyrosine. This deficiency leads to a buildup of toxic substances in the body, causing various health issues.
Genes Involved
Tyrosinemia Type I is caused by mutations in the FAH gene, located on chromosome 15. This gene provides instructions for making the FAH enzyme. Mutations in this gene lead to a deficiency in the enzyme, resulting in the buildup of toxic substances.
Recognizing the Signs and Symptoms
The symptoms of Tyrosinemia Type I can vary depending on the severity of the condition and the age of onset. Common symptoms include:
- Liver dysfunction: Jaundice (yellowing of the skin and eyes), enlarged liver, liver failure.
- Kidney problems: Kidney failure, kidney stones.
- Neurological issues: Seizures, developmental delays, mental retardation.
- Other: Vomiting, diarrhea, poor weight gain, bone marrow problems, and an odor of cabbage or burnt sugar in the breath.
Causes
Tyrosinemia Type I is inherited in an autosomal recessive pattern. This means that both parents must carry a copy of the mutated FAH gene for their child to inherit the disorder. If only one parent carries the gene, their child will be a carrier and may not show any symptoms but can pass the gene to their children.
Inheritance/recurrence risk
The risk of a couple having a child with Tyrosinemia Type I depends on their genetic carrier status. If both parents are carriers, there is a 25% chance their child will have the disorder. Genetic testing can determine carrier status and help families make informed decisions about family planning.
