[2] Patients present with symptoms reflecting the decreased production of dopamine: hypokinetic-rigid syndrome, dystonia, complex encephalopathy.

[1] According to the classification on GeneReviews,[3] three approximate phenotypes could be discerned: In order to diagnose tyrosine hydroxylase deficiency, a sample of the patient's cerebrospinal fluid may be obtained to assess neurotransmitter metabolites that may be affected, as illustrated by the metabolic links in Figure 1.

[1] Upon finding a pattern of CSF abrormalities suggestive of the disease, the diagnosis may be confirmed by analysing the TH gene encoding the enzyme.

[1] According to a review of dopa-responsive dystonias published in 2021, tyrosine hydroxylase deficiency may be hard to diagnose, with a median diagnostic delay of 4 years,[2] and misdiagnosis happens in a significant proportion of patients, with cerebral palsy being the most common erroneous diagnosis.

[1] The first case reports of "Segawa syndrome" and parkinsonism caused by mutations in the tyrosine hydroxylase gene were published in 1995[1][4] and 1996.