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Dopa-responsive Dystonia
GCH1 (Cyclohydrolase I)
TH (Tyrosine Hydroxylase)
GTP Cyclohydrolase I Deficiency
GCH1 (Cyclohydrolase I)
Tyrosine Hydroxylase Deficiency/ Autosomal Recessive Infantile Parkinsonism
TH (Tyrosine Hydroxylase)
Dopa-Responsive Dystonia (DRD) is a treatable neurological condition, which can present with a variety of symptoms ranging from dystonia, spastic paraparesis, and proximal weakness to parkinsonism. The majority of mutations in DRD involve the GCH1 gene. GCH1 mutations are dominantly inherited. The recessive form of DRD is associated with mutations in the TH gene.
The only gene causing GTP Cyclohydrolase I Deficiency is the GCH1 gene. GTP Cyclohydrolase I Deficiency is an autosomal recessive disorder of the BH4 biosynthesis pathway presenting with hyperphenylalaninemia (HPA) associated with monoamine neurotransmitter deficiency.
GeneDx offers sequence analysis of the TH gene in association with Tyrosine Hydroxylase deficiency/ Autosomal Recessive Infantile Parkinsonism. Tyrosine hydroxylase (TH) deficiency is an extremely rare autosomal recessive disorder associated with wide phenotypic variability ranging from mild dopa-responsive dystonia to an infantile parkinsonism with or without encephalopathy that may be unresponsive to levodopa treatment.
Sequence analysis of the GCH1 and/or the TH genes can be ordered on a single specimen, together or alson in association with Dopa-responsive Dystonia. For Autosomal Dominant Dopa-responsive Dystonia, targeted array CGH analysis (ExonArrayDx) can be ordered to evaluate for a deletion or duplication of one or more exons of the GCH1 gene if no mutation is found by sequencing. Full sequence analysis of the GCH1 and TH genes is available in association with GTP Cyclohydrolase I Deficiency and Tyrosine Hydroxylase Deficiency/ Autosomal Recessive Infantile Parkinsonism respectively.
The preferred specimen type for optimal turn-around time is blood (EDTA, 1-5 mL), but buccal (cheek) brushes will be accepted. For more details see the linked Information Sheets below.
GCH1 Information Sheet, including prices and CPT codes
GCH1 Consent Document
TH Information Sheet, including prices and CPT codes
TH Consent Document
Genetic Test Sample Submission Form (Test Requisition Form) including Payment Options
Dopa-responsive, dystonia, DYT5, GCH1, GTP cyclohydrolase 1, parkinsonism, Parkinson’s disease, diurnal fluctuation, levodop, cerebral palsy
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