The Melanocortin 1 Receptor (Mc1r) Variants Do Not Account for the Co-occurrence of Parkinson's Disease and Malignant Melanoma

Parkinson’s disease (PD) is characterized by loss of melanin-positive dopaminergic neurons in the substantia nigra. Malignant melanoma (MM), a melanocyte-derived neoplasm, occurs with higher than expected frequency among PD patients. Red-haired individuals exhibit a threefold risk for developing MM than dark-haired people; PD risk also increases with lighter hair color. One plausible explanation for the associations between MM, hair color, and PD is the melanocortin-1 receptor (MC1R) gene that plays a key role in hair and skin pigmentation as well as in MM predisposition. We hypothesized that specific MC1R variants may predispose to both MM and PD. Genotyping of the MC1R gene was performed for 16 PD patients with MM (PD+ MM+) and for three sets of age, sex, and ethnically matched controls, including 36 patients with PD (PD+ MM−), 37 with MM (PD− MM+) and 37 with neither diagnosis (PD− MM−). No association was found between MC1R variants and the co-occurrence of PD and MM. The risk for MM was higher in carriers of two MC1R variants versus with no MC1R variant (odds ratio (OR) = 5.0, 95 % confidence interval (CI) 1.7–14.4, p = 0.003). The risk for PD in carriers of two MC1R variants was markedly lower (OR = 0.213, 95 % CI 0.063-0.725) compared with individuals with no MC1R variant (p = 0.013). In this study, MC1R variants were not associated with both MM and PD. Further studies in larger cohorts are necessary to confirm these preliminary results.