Background: In a recent study, the link between Parkinson disease and malignant melanoma in patients was also observed in nuclear families, suggesting a possible genetic link between the 2 diseases.
Methods: To clarify the strength of the association, we used the nationwide Danish cancer and population registers to identify 8567 parents and 7310 siblings of patients in whom malignant melanoma was diagnosed at age 50 years or less. Hospital register data were used to follow relatives for a primary diagnosis of Parkinson disease between 1977 and 2008, and to calculate hospitalization rates for Parkinson disease in the general Danish population for comparison. Similarly, cancer registry data were used to trace cases of malignant melanoma.
Results: The hospitalization rate ratio for Parkinson disease among the melanoma cohort was slightly increased (ratio of observed to expected hospitalizations = 1.2 [95% confidence interval = 0.9-1.5]) on the basis of 54 observed cases. In contrast, the risk among relatives for malignant melanoma was markedly increased. There was no overlap between families affected by multiple cases of Parkinson disease and those affected by multiple cases of malignant melanoma.
Conclusions: For the age range investigated, our data do not support a genetic link between Parkinson disease and malignant melanoma.