excerpt:
"Like all epidemiology studies, this study raises new questions for research. First, it remains unknown why rosacea and PD are linked. Inflammation, for example, is implicated in both PD and rosacea, and the two share a particular molecular pathway involved in inflammation associated with molecules known as matrix metalloproteinases. The study authors suggest that future investigations could focus on this and other potential commonalities, including genetics. In addition, the researchers observed a slightly reduced risk for PD among those who were treated with an antibiotic agent that modifies the immune system, tetracycline..."

http://www.pdf.org/en/science_news/r.../pr_1458570982