1 in 2 chance of inheriting a normal copy of FAH from one parent, and a defective copy from the other. These children will be carriers. They will not have tyrosinemia, but they will have a 1 in 2 chance of passing the defective gene to each of their children. FAH is an enzyme involved in the metabolism of the essential amino acid phenylalanine. An enzyme is a type of protein which catalyzes chemical reactions.
Metabolism refers to the building up and breaking down of biochemical products.
Amino acids are the building blocks of proteins. In tyrosinemia, low levels of FAH result in a buildup of metabolic intermediates in the biochemical pathway by which phenylalanine is normally processed. This buildup of metabolites is toxic, causing damage to many tissues, primarily the liver and kidneys. In acute tyrosinemia, signs and symptoms occur within the first few months of life. In chronic tyrosinemia, symptoms develop more gradually and are less severe.