Nearly a decade ago, Karen Douthitt and her sisters June Ward and Susie Gilliam set out to learn why Alzheimer's disease was affecting so many of their family members. Since then, each sister has found out whether she carries a rare gene mutation that makes Alzheimer's inescapable. Jon Hamilton talks to Emily about the sisters and how all three have found ways to help scientists trying to develop treatments for the disease. Thoughts or comments? Get in touch — we're on Twitter @NPRShortWave and on email at shortwave@npr.org.