Question: what are the rare types of dementia?
Answer: Atypical Alzheimer's disease. — Frontal variant Alzheimer's disease (fvAD) ... 
CADASIL.
Corticobasal syndrome (CBS)
Creutzfeldt–Jakob disease (CJD)
HIV-associated neurocognitive disorder (HAND)
Huntington's disease.
Normal pressure hydrocephalus (NPH)
Progressive supranuclear palsy (PSP)