TOR1A and Parkinson disease: At least two different genetic dystonia forms are currently known to be caused solely or primarily by such single founder variants: X-linked dystonia–parkinsonism (XDP; DYT/PARK-TAF1) (Lee et al. 1976) and TOR1A-variant related isolated dystonia (DYT-TOR1A) (Ozelius et al. 1997).