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Melanoma and Parkinson’s — New Evidence Makes a Surprising Connection

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Family History of Melanoma Boosts Risk for Parkinson’s Disease

Melanoma, the most serious form of skin cancer, and Parkinson’s disease may seem an unlikely pairing, but researchers have found a strong link between the two. Further investigation into data from several older studies — specifically the Health Professionals Follow-up Study and the Nurses’ Health Study — together covering about 132,000 men and women, found that people whose parents or siblings had  melanoma are nearly twice as likely to develop Parkinson’s.

The lead author of the study, Xiang Gao, MD, PhD, of Harvard Medical School, has long been investigating how melanin, which creates pigmentation, relates to Parkinson’s disease. He speculates that the two diseases share common genetic components. In a previous study, Dr. Gao found that having light hair (a known risk factor for melanoma) puts people at twice the risk for Parkinson’s. Dark-skinned races have the lowest incidence of Parkinson’s, while Caucasians are at the highest risk.

What Does It Mean?

I called Dr. Gao to learn more about how all of this comes together. He explains that there is a small structure in the mid area of the brain called the substantia nigra — it contains most of the brain’s dopamine and its main function concerns body motion. Hallmarks of Parkinson’s disease include loss of dopamine and highly impaired motor function. In people who do not have Parkinson’s disease, the substantia nigra is dark because it contains a high level of melanin, whereas in people with Parkinson’s, the area fades to gray or white.

People with light skin and red hair likely produce less melanin — and we now know they are at higher risk for Parkinson’s and melanoma. Dr. Gao believes this points to a connection between the two, though it’s unclear exactly what it is or how it works. The researchers are hoping that uncovering the genetic determinants of melanoma could help identify genes for Parkinson’s, which could in turn open up the possibility of gene therapy for Parkinson’s. Before that happens, though, other studies will have to replicate these findings, he says, and further studies will also need to determine if there are other melanoma-related genes involved. In the meantime, this is an intriguing area of study and I’ve asked Dr. Gao to keep me informed as more information becomes available.

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Source: Xiang Gao, MD, PhD, instructor in medicine, Harvard Medical School, and associate epidemiologist, Brigham and Women’s Hospital, both in Boston. Date: December 31, 2009 Publication: Bottom Line Health
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