The fact that human variants in the α-syn gene SNCA (PARK1), or multiplications of the SNCA locus, underpin autosomal dominant parkinsonism supports a common etiology between sporadic PD and inherited parkinsonian disorders, and there is mounting evidence that other PARK gene variants also contribute to sporadic PD (Jankovic, 2008; Kim et al., 2024; Nalls et al., 2011; Do et al., 2011). Here, SNCA is linked to parkinsonian disorder.