GCH1 mutations are common in Serbian patients with dystonia-parkinsonism: Challenging previously reported prevalence rates of DOPA-responsive dystonia.
In this model we show that these features evolve without dopaminergic neurodegeneration, suggesting that postsynaptic plasticity, rather than presynaptic degeneration, may contribute to the development of parkinsonism in patients with l-dopa-responsive dystonia.
Mutations in the GCH1 gene are the most common cause of DRD, however, in some cases when the disease is associated with parkinsonism mutations in the PARK2 gene may be identified.
We describe clinical, genetic and nigrostriatal dopaminergic imaging ([(123)I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) tropane single photon computed tomography) findings of four unrelated pedigrees with DOPA-responsive dystonia in which pathogenic GCH1 variants were identified in family members with adult-onset parkinsonism.
Patients with mild parkinsonian symptoms, excellent response to low dosages of dopaminergic drugs and a reduced dopamine-transporter uptake in [(123)I] FP-CIT-SPECT might more commonly be GCH1 mutation carriers than has previously been supposed.
Patients with the dystonia plus syndrome DYT5 display levodopa-responsive dystonia sometimes associated with tremor or parkinsonism (DYT5a, mutations in GCH1); a more severe phenotype with psychomotor involvement can be seen in recessive forms (DYT5b with TH mutations, SPR-deficiency syndrome).
The clinical presentations of patients with mutations in TH and SPR genes were strikingly more complex, characterized by mental retardation, oculogyric crises and parkinsonism and they were all classified as Dopa-responsive dystonia-plus syndromes.
Dopa-responsive dystonia (DRD), also known as Segawa syndrome or hereditary progressive dystonia with diurnal fluctuation, is clinically characterized by the occurrence of simultaneous or late Parkinsonism and by an excellent response to treatment with low doses of L-dopa.
Collaborative study.Patients Eight patients from Sudan with particularly early onset (ages 9-17 years) and phenotypes varying from dopa-responsive dystonia-like to typical early-onset parkinsonism.
Arg(184)His mutant GTP cyclohydrolase I, causing recessive hyperphenylalaninemia, is responsible for dopa-responsive dystonia with parkinsonism: a case report.
The majority of our parkin-associated cases were characterized by early-onset dopa-responsive parkinsonism with benign course and slow progression (5 patients from two families have been followed for as long as 18-36 years), and 1 patient had a phenotype of dopa-responsive dystonia.
The dystonia-plus group is defined by the association of parkinsonism (dopa-responsive-dystonia and rapid-onset dystonia-parkinsonism) or myoclonus (myoclonus-dystonia).
The associated phenotypical spectrum encompasses early onset, levodopa-responsive parkinsonism (average onset in the early 30s in Europe), and it overlaps with dopa-responsive dystonia in cases with the earliest onset, and with clinically typical Parkinson's disease in cases with later onset.
It is also clear that notwithstanding the discovery of GCH1 and hTH mutations responsible for DRD, there remain many important unresolved issues regarding this disorder, including questions of female predominance, phenotypic heterogeneity, and presence of childhood-onset dystonia versus the expected parkinsonism resulting from a striatal DA deficit.
In contrast, no mutations in any exons of the GTP-CH I gene were found in 2 patients with early-onset parkinsonism with dystonia (EOP-D) who developed dopa-responsive parkinsonism and dystonia at 6 and 8 years old, respectively.
We conclude that so far there is no evidence that mutations of the GTPCH gene are responsible for the development of parkinsonism in patients without a positive family history of DRD.