My oldest sister died of AD at age 56, having been struck with it about age 40. You are correct in that it can run in families especially if there is a Maternal X link. All of us sister had boy children, so the link is now gone, thank God. The rest of us sisters are all over 55 yoa, so we know we won’t get the early onset if we get it at all.
So Alz. can be gender specific too, huh? Well, learn something new everyday. I guess it would be seen as a ‘recessive trait’ to be stored in the DNA. This exists in my family too, but ‘back then’ 1960-1980’s people in my family just didn’t talk much about it, and we kids were under orders not to ask. I think more people are ready to discuss it today, which is the healthier way.