Tyrosine Hydroxylase Deficiency

Tyrosine hydroxylase (TH) deficiency is a rare autosomal recessive movement disorder with onset typically within the first years of life. It is associated with phenotypic variability that ranges from dopa-responsive dystonia (DRD) to dopa-responsive infantile parkinsonism to infantile progressive encephalopathy that is not dopa-responsive. Additional features may include hypotonia, hypokinesia, oculogyric crises and ptosis, and autonomic signs (temperature instability, hypoglycemia). A diurnal fluctuation of symptoms may be evident. Carriers are usually asymptomatic but some have been reported with restless leg symptoms and exerciseinduced stiffness. TH deficiency is typically characterized by decreased levels of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) with normal levels of 5-hydroxyindoleacetic acid (5-HIAA) and a decreased HVA/5-HIAA ratio in cerebrospinal fluid. There is no specific biochemical test for this disorder. TH deficiency is caused by mutations in the TH gene on chromosome 11p15.5. Definitive diagnosis requires the identification of mutations in the TH gene. The phenotype associated with TH deficient doparesponsive dystonia may significantly overlap with DRD caused by GCH1 gene mutations, but may also be more complex (DRD-plus syndrome). Molecular testing of the TH gene should be undertaken in patients with a complex DRD presentation, and in patients negative for a GCH1 gene mutation with simple DRD. Mutation analysis of the GCH1 gene is available at GeneDx

Tests Available

Forms and Documents

Test Details

  • Confirmation of a clinical diagnosis
  • Identification of at-risk family members


3 weeks
2-5 mL Blood - Lavender Top Tube
Buccal Swabs

*Reporting times are typical, but could be extended in situations outside GeneDx's reasonable control.


  • 348.3 Encephalopathy, not elsewhere classified
  • 780.6 Fever and other physiologic disturbances of temperature regulation
  • 251.2 Hypoglycemia, unspecified Hypoglycemia: NOS reactive spontaneous
  • 374.3 Ptosis of eyelid
  • 781 Symptoms involving nervous and musculoskeletal systems Excludes: depression NOS (311) disorders specifically relating to: back (724.0-724.9) hearing (388.0-389.9) joint (718.0-719.9) limb (729.0-729.9) neck (723.0-723.9) vision (368.0-369.9) pain in limb (729.5)
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**The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.


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