Tyrosinemia type 1 is a genetic disorder caused by a mutation in the gene for the FAH enzyme, which is needed to break down tyrosine. It is inherited in a recessive manner. Recessive means that parents of a child with this disorder each carry one copy of the mutated gene but show no signs or symptoms of the condition themselves.
Boys and girls are affected in equal numbers.
For a child to be affected, both parents have to pass on one copy of the defective gene to the child. The risk of their child having hereditary tyrosinemia type 1 is 25%.
Orfadin is a synthetic reversible inhibitor of 4-hydroxyphenylpyruvate dioxygenase indicated for use as an adjunct to dietary restriction of tyrosine and phenylalanine in the treatment of hereditary tyrosinemia type 1 (HT-1).