MC1R and Parkinson disease: Second, subgroups with limited sample sizes, including participants homozygous for high-penetrance MC1R variants (n=17), those with rare MC1R variants such as D84E (n=4) and R142H (n=3), and those with prodromal PD (n=45), limited statistical power to detect genotype differences, variant-specific associations, or differences in the risk of phenoconversion.