Alzheimer's is an acquired neurodivergence.

So adult onset dyslexia would not indicate autism. It would be classified as acquired neurodivergence? 

Do I have this right? 

That's right. Adult onset dyslexia would be considered aquired and a Learning Disorder. I don't know the exact circumstances but a lot of people slipped through the public school system before the '90's (when the IDEA special ed laws were passed) without being diagnosed with a learning disorder.

So if the person wasn't dyslexic as a youth then something happened to their brain as an adult to cause them to mix up letters and have trouble with word cognition.

Another thing to think about with neurodivergence is early intervention to take advantage of neuroplasticity. In other words the sooner a child is diagnosed and receives intervention for whatever reason the easier it is to overcome and retrain the brain. 'Birth To Three' is what it's called in New England.

But you're talking about adults...