Tyrosine Hydroxylase Deficiency

Tyrosine hydroxylase (TH) deficiency is a rare inherited condition that affects the nervous system. There are three different forms of the condition that vary in severity. The mild form is called TH-deficient dopa-responsive dystonia and typically develops between age twelve months and six years. The two severe forms, which are called infantile parkinsonism and progressive infantile encephalopathy, often begin shortly after birth or during early infancy. Although there is some overlap of features among the three forms, each is associated with unique signs and symptoms. TH deficiency is caused by changes (mutations) in the TH gene and is inherited in an autosomal recessive manner. Affected people are usually treated with levodopa therapy.