Polymorphisms in genes encoding dopamine receptors (Lee et al., 2009; Zainal Abidin et al., 2015; Krishnamoorthy et al., 2016; Erga et al., 2018; McDonell et al., 2018; Redenšek et al., 2020), dopamine transporters (Cilia et al., 2016; Cormier-Dequaire et al., 2018; Redenšek et al., 2019, 2020), and proteins involved in dopamine metabolism (Ziegler et al., 2014; Kraemmer et al., 2016; Jesús et al., 2020) have been linked to increased PD + ICD risk. The gene discussed is SLC6A3; the disease is Parkinson disease.