POLG and Parkinson disease: More than 300 pathogenic mutations have been mapped to the POLG gene based on the Human DNA Polymerase Gamma Mutation Database, and both homozygous and heterozygous POLγA mutations have been found in individuals ranging from newborns with myocerebrohepatopathy spectrum (MCHS) to the elderly with Parkinsonism (Tzoulis et al., 2013; Hikmat et al., 2017; Rahman and Copeland, 2019).