Dementing illnesses comprise Alzheimer's disease (AD), Pick's disease, Multi infarct dementia (MID) and other neurological disorders. These diseases have different clinical characters respectively.

Pick's disease is described as a rare, progressive, degenerative disease, mostly involving the frontal and temporal lobes. This was first described by Arnold Pick in 1892.

Pick's disease is a diagnosis of exclusion, and reversible causes of dementia should be sought out first.