Odd correlation: Parkinson’s disease and melanoma. What is the possible link?

Abstract

Parkinson’s disease (PD) is a neurodegenerative disorder, characterised by depletion of dopamine in the striatum and loss of melanin-positive, dopaminergic neurons in the substantia nigra. Melanoma is a skin neoplasm arising from epidermal melanocytes. The epidemiology of melanoma focuses on well-known risk factors such as light skin and hair colour, gender, eye pigmentation, and ultraviolet (UV) exposure. Many studies have suggested an association between Parkinson’s disease and melanoma. The mechanism underlying the possible connection between PD and melanoma is not clear and has aroused lots of interest. More interesting is that the link between these two diseases runs both ways. What is the underlying cause of this reciprocal association? Is it due to Parkinson’s treatment? Is levodopa the reason for increased incidence of melanoma in people with the neurodegenerative condition? Are there any genetic, immune system irregularities or environmental risk factors that serve as the common denominator between these two conditions? Should we consider melanoma comorbidity with Parkinson’s disease and vice versa? Some hypotheses include pigmentation changes in melanin and/or melanin synthesis enzyme like tyrosinase hydroxylase, autophagy deficits, disturbed form of metabolically controlled cell death, and changes of PD-related genes such as Parkin or a-synuclein. Learning more about the relationship between PD and melanoma may lead to a better understanding of each disease and contribute to more effective treatments of both.