Table 3. Clinical and laboratory features of dystonias that are responsive to dopaminergic drugs.
| Categories | # of cases | Clinical features | Laboratory features | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Response to L-dopa | Usual age of onset | Main phenotype | Additional features | DAT imaging | Genetic diagnosis | ||||
| Involving dopaminergic system, Non-neurodegenerative | |||||||||
| Enzymatic defects in dopamine synthetic pathway | |||||||||
| 1) DRD phenotype | Large | ++++ | Child-adole | DRD | Diurnal fluctuation, rare levodopa-related motor complications | NL | GCH-1, SR, TH | ||
| 2) DRD-plus phenotype | Large | ++ | Infancy | DRD-plus | Diurnal fluctuation, hypotonia, levodopa-related motor complications, parkinsonism, oculogyric crises, convulsions, developmental delay, myoclonus | Pro-NLa | GCH-1, PTPS, SR, DHPR, TH, AADC | ||
| Transportopathy | |||||||||
| 1) DAT deficiency | Small | + | Infancy | DRD-plus | Parkinsonism, hypotonia, levodopa-related motor complications, developmental delay, pyramidal tract signs, ocular flutter, saccadic initiation defect | AbNL | SLC6A3 | ||
| 2) VMAT2 deficiency | Small | + | Infancy | DRD-plus | Parkinsonism, developmental delay, oculogyric crisis, excessive diaphoresis, ptosis, hypotonia, ataxia, limited upward gaze | Pro-NLa | SLC18A2 | ||
| Developmental disorders affecting dopamine system | |||||||||
| 1) SOX6 mutation | Small | ++ | Child-adole | DRD-plus | Development delay, dysmorphism, splenomegaly, sternal deformity, slow saccades, athetoid movement, resting/action tremor | Pro-AbNLa | SOX6 | ||
| Involving dopaminergic system, neurodegenerative | |||||||||
| Juvenile Parkinson's disease | Large | ++++ | Child-adole | DRD | Parkinsonism, long-term levodopa-related motor complications | AbNL | PARKIN, DJ1, PINK1 | ||
| Juvenile Parkinson's disease by SYNJ1 mutation | Small | +++ | Adole-adult | DRD-plus | Parkinsonism, dystonia, hypotonia, tremor, postural instability, seizure, cognitive impairment | AbNL | SYNJ1 | ||
| Pallidopyramidal syndrome | Large | ++ | Child-adole | DRD-plus | Parkinsonism, pyramidal tract signs, developmental delay, neuro-psychiatric symptoms | AbNL | PLA2G6, FBX07, ATP13A2, SPG11, WDR45, C19orf12 | ||
| Special findings on brain MRI according to subtypes | |||||||||
| Spinocerebellar ataxia type 3b | Small | +++ | Adult | DRD | diurnal fluctuation | Pro-AbNLa | ATXN3 | ||
| Others, non-neurodegenerative | |||||||||
| DYT1 b | Small | ++ | Child-adole | DRD | - | Pro-NLa | TOR1A | ||
| GLUT1 deficiency syndromeb | Small | ++ | Child | DRD | Paroxysmal exercise-induced dystonia, short lasting | NL | SLC2A1 | ||
| Myoclonus-dystoniab | Small | ++ | Child | DRD-plus | Myoclonus, alcohol response, psychiatric symptoms | Pro-NLa | SGCE | ||
| Others, neurodegenerative | |||||||||
| Ataxia telangiectasiab | Small | ++ | Child-adole | DRD | Torticollis, laryngeal dystonia, postural hand tremor | Pro-NLa | ATM | ||
| Others, undetermined | |||||||||
| Dopa-responsive camptocormiab | Small | +++ | Adult | DRD | Diurnal fluctuation, no motor complications | NL | unknown | ||
L-dopa = levodopa, DAT = dopamine transporter, DRD = dopa-responsive dystonia, Child = childhood, Adole = adolescence, NL = normal, Pro-NL = probably normal, AbNL = abnormal, VMAT2 = vesicular monoamine transporter 2, Pro-AbNL = probably abnormal, GLUT1 = glucose transporter 1.
aPro-NL and Pro-AbNL are presumptive descriptions based on patho-mechanism; bDystonia with dopa-responsiveness is only an infrequent manifestation in that disease.