GCH1 and dopa-responsive dystonia: Similarly, a childhood-onset foot dystonia, spreading cranially to become generalized dystonia with concomitant mild parkinsonism, diurnal fluctuations of symptoms, and excellent response to l-dopa, is highly indicative of dopa-responsive dystonia (DRD; DYT/PARK-GCH1) resulting from pathogenic variants in the GCH1 gene (Weissbach et al. 2020).