New York Times article on inheritable dementia - eviltoast
The Vanishing Family
www.nytimes.com
They all have a 50-50 chance of inheriting a cruel genetic mutation — which means disappearing into dementia in middle age. This is the story of what it’s like to live with those odds.

“The Vanishing Family.” This is a “gift” link, so you shouldn’t hit a paywall; let me know if you have any problems.