Echo of my experience. My wife’s elderly mother did not have any classic form of dementia, and could verbally convince many people for a while, including doctors and my wife’s older sister, that she was rational and capable.
But in fact she had no short term memory at all and was incapable of taking care of herself. She was terrified of being ‘put in a home’, and was able to put up a front for a while to stave it off.
Sometimes you should override what they say if you have to. I wish we had done so (and ignored BS from older sister). It would have been better for everyone, in retrospect.
My sister is just now putting her husband into a care facility (advanced Huntington’s). He does not know yet. But after several years - including daily aides - she just can’t take it anymore.
I worked for a while with a woman who had early-stage Huntington’s. Her father was thought to have Alzheimer’s until SHE got her diagnosis! Thankfully, she never had children of her own.
Sis and BIL have 3. No idea if the kids have tested. I know at least one of them is currently discussing having kids. Every one of BIL’s sibs died of it. Quite the nightmare.
My understanding was that at one point he expressed an intention of starving himself - as his sister had. Apparently he has changed his mind. I imagine when he is in a facility they will just strap him into a chair and let him sit there. Ugh!
The sad thing is that symptoms usually don’t appear until well into or after child-bearing years. Now. you can be genetically tested. I would certainly do so before even thinking about having biological children.
That a few days of IV fluids and antibiotics brings them back to rationality.