Thirteen studies explored genetically homogeneous cohorts, involving DYT1 (TorsinA mutation) (n = 3) and DYT6 (THAP1 mutation) (n = 1, or both n = 2), DYT3 (n = 2), X‐linked dystonia parkinsonism (DYT12, ATP1A3 mutation, n = 2), myoclonus dystonia (DYT11, SGCE mutation, n = 2) and DYT27 (n = 1). The gene discussed is THAP1; the disease is myoclonus-dystonia syndrome.