Deadly Disordered Pair

Scientists are linking more and more diseases together - autism and epilespy, gum disease and heart disease, type 1 diabetes and celiac disease. New evidence suggests another pairing.

People living with Parkinson's Disease are twice as likely to have melanoma as people without the neurological disorder, according to a new study. Melanoma is the most serious and deadliest form of skin cancer.

Parkinson's patients should check for melanoma regularly.

While both diseases are fairly rare, and the reason for the link is unknown,  researchers say the evidence is solid. Dr. Honglei Chen, an investigator at the National Institute for Environmental Health Sciences, and colleagues analyzed the results of 12 previous studies looking at the association between the two conditions. All but one found increased risks.

The lead study author, Chen says these findings suggest that people with Parkinson's pay particular attention to their skin health. Annual skin cancer screenings would be wise.

It's not known whether either disease causes the other, and there's no order of onset. People living with melanoma can later develop Parkinson's and vice versa. Distinguishing such a pattern will be difficult because both disorders can take years to develop, says Dr. John Bertoni, a professor of neurology and director of the Parkinson’s Disease Clinic at the University of Nebraska Medical Center,

Dr. Bertoni's earlier research was included in this analysis. He and his team found 24 cases of melanoma after screening 2,100 people with melanoma. That's twice the rate found in the healthy population.

Unanswered questions remain, including why the two conditions are associated. Chen says there may be genetic links, or perhaps melanoma and Parkinson’s disease have related pathways.

The study was published in the journal Neurology.