Mondo Description Tyrosine hydroxylase (TH) deficiency is an autosomal recessive disorder characterized by a spectrum of phenotypic features, based on severity and response to levodopa. It can be broadly categorized into TH-deficient dopa-responsive dystonia (mild, with dramatic and sustained response to levodopa), TH-deficiency infantile parkinsonism with motor delay (severe, with incomplete response to levodopa), and TH-deficiency infantile encephalopathy (very severe, with little to no response to levodopa).