Table 2. New definitions of DRD, DRD-plus, and DRD look-alike.

Previous name	Previous definition4,21	New definition
DRD	A syndrome of selective nigrostriatal dopamine deficiency caused by genetic defects in the dopamine synthetica pathway without nigral cell lossa	A group of non-neurodegenerative disorders by genetic defects involving nigrostriatal dopaminergic system with cardinal manifestationsb (namely, DRD phenotype)
DRD-plus	A group of disorders caused by genetic defects in the dopamine synthetica pathway without nigral cell lossa that have features of DRD ‘plus’ those features that are not seen in DRD	A group of non-neurodegenerative disorders by genetic defects involving nigrostriatal dopaminergic system with dopa-responsiveness plus additional featuresc (namely, DRD-plus phenotype) that are not seen in DRD
DRD look-alike	-	A group of 1) neurodegenerative or non-neurodegenerative disorders without involving the nigrostriatal dopaminergic system or 2) neurodegenerative disorders with involving nigrostriatal dopaminergic system, that could present with dystonia responsive to dopaminergic drugs

DRD = dopa-responsive dystonia.

^aWhich are deleted in the new proposal to include additional disorders; ^bThose include dystonia and/or parkinsonism, and dramatic response to levodopa without long-term motor complications; ^cThose include infantile onset, developmental delay, psychomotor retardation, seizure, hypotonia, drowsiness, recurrent hyperthermia, ptosis, cerebellar dysfunction, poor responsiveness to levodopa or other dopaminergic drugs.