Biology's hand in history: did genetic disease add fire to America's most famous feud?

For generations, the Hatfields and McCoys fought to the death over land rights, timber, and just about everything else. Now, doctors have one possible explanation for the virulence of the legendary feud that broke out in the 1880s between these two Appalachian families.

Researchers have been studying the McCoy family for several decades, because a disorder called von Hippel-Lindau disease (VHLD) occurs at extremely high rates in members of this family. The disorder causes both benign and cancerous tumors, and when these tumors arise in the adrenal gland-where they are called pheochromocytomas-they can cause high levels of stress hormones and symptoms including extreme irritability or anxiety, fast heartbeat, high blood pressure, and severe headaches.

Members of the extended McCoy family recently came forward to make this information public, so that other family members can seek treatment. Revi Mathew, a Vanderbilt University endocrinologist treating one family member, says, "This condition can certainly make anybody short-tempered, and if they are prone because of their personality, it can add fuel to the fire."

Rita Reynolds, a McCoy descendent who has the disease, says that doctors studying the family over the decades referred to their condition as "madness disease." (To protect the family's privacy, doctors referred to them in medical journals as the "McC kindred.") Reynolds adds, "Our family would just go off, even on the doctors."