I found this story on how the long-lived Hatfield and McCoy feud might have been fueled in part by a genetically inherited disease known as Von Hippel-Lindau Syndrome that was passed down through the McCoy family somewhat interesting. The disease increases blood pressure, stimulates frequent fits of anger and hostility, and eventually leads to tumors and death.
I wonder who else has this syndrome?
In all seriousness, it sounds like a terrible disorder.
Here's link to the story:
Disease underlies Hatfield-McCoy Field