It's not Alzheimer's

Frontotemporal dementia (frontotemporal lobar degeneration) is an umbrella term for a diverse group of uncommon disorders that primarily affect the frontal and temporal lobes of the brain, the areas generally associated with personality, behavior and language, according to the Mayo Clinic definition page.

Here's what else it says:

In frontotemporal dementia, portions of the frontal and temporal lobes atrophy, or shrink. Signs and symptoms vary, depending upon the portion of the brain affected.

Some people with frontotemporal dementia undergo dramatic changes in their personality and become socially inappropriate, impulsive or emotionally blunted, while others lose the ability to use and understand language.

Frontotemporal dementia is often misdiagnosed as a psychiatric problem or as Alzheimer's disease. But frontotemporal dementia tends to occur at a younger age than does Alzheimer's disease, typically between the ages of 40 and 70.