Parkinson Disease and Melanoma May Share a Genetic Link

Summary and Comment |
September 28, 2012

Parkinson Disease and Melanoma May Share a Genetic Link

  1. Hensin Tsao, MD, PhD

Reciprocal predispositions of parkinsonism and cancer demonstrate a strong association between these conditions.

  1. Hensin Tsao, MD, PhD

Persons with Parkinson disease (PD) have a lower than expected prevalence of most cancers, but melanoma is an exception. Several studies have found an elevated risk for malignant melanoma in PD patients. A reciprocal increased risk for PD has been reported in melanoma patients and their first-degree relatives, suggesting a common genetic or environmental link. Researchers used the Utah Cancer Registry and the Utah Population Database, which contains birth, death, and family relationship data of more than 2 million individuals, dating back in some instances 15 generations, to assess associations between PD and cancer subtypes.

Among 388,221 individuals with a recorded cause of death and at least three generations of genealogic data, 2998 had PD as a cause of death, and 48 of these had melanoma, versus an expected rate of 24.6 (relative risk, 1.95; 95% confidence interval, 1.44–2.59). Statistically significant excess risk for melanoma was found in the first- and second-degree relatives of those with PD-related deaths. Among 7841 individuals with a melanoma diagnosis and at least three generations of genealogy, the researchers found significantly increased risk for PD-related death in the melanoma cases (RR, 1.65; 95% CI, 1.22–2.19) and in their first-, second-, and third-degree relatives. Prostate cancer was the only other cancer observed in excess in those with PD-related death. Among those with PD-related deaths, men had significantly fewer than expected lung, pancreas, and stomach cancers, and colon cancers were significantly decreased in women. The authors conclude that the findings in this study strongly support the hypothesis of a common genetic link between PD and melanoma.

Comment

This study adds further genetic evidence of a link between Parkinson disease and melanoma. The strength of this association is indicated by the finding of an increased risk in both directions: an increased risk for melanoma among PD patients and vice versa. I personally have several patients who have been diagnosed with both conditions, and the question of Sinemet treatment invariably surfaces at some point. Because PD patients tend to be older, quality of life becomes a real issue for them. I typically balance the risk of their melanoma with disability if Sinemet is discontinued. If they remain on the drug, careful melanoma follow-up is certainly indicated.

Citation(s):

Reader Comments (1)

David L. Keller

1) Was the expected rate of melanoma of 24.6 computed for sunny Utah, or is it a national figure? If the latter, then the increased risk of melanoma in Parkinson patients in Utah might be due to the higher-than- average sun exposure in that state.

2) Sinemet ingestion might explain the increased risk of melanoma in Parkinson patients, but it would not explain the increased risk of Parkinson's in melanoma patients.

Competing interests: None declared

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