GNAL and Dystonia: A single gene can be associated with multiple clinical presentations (phenotypic pleiotropy – e.g. ADCY5 gene variants that can manifest with chorea, dystonia and myoclonus in variable association, or ANO3 and GNAL gene variants, previously classified as isolated dystonia, can also present with dystonia and myoclonus), while similar phenotypes may result from variants in different genes (genetic heterogeneity – e.g. cerebellar ataxia, myoclonus epilepsy syndrome etc.).