Pick's disease is a rare (less than 30 cases per 100,000) form of progressive fronto-temporal-lobe dementia first described by Czech neurologist and psychiatrist Arnold Pick in 1892.

It tends to affect those under 65 and is typified by symptoms such as hesitant speech, difficulty articulating, stuttering, difficulty recalling words or names, and behavioral and personality changes. Later stages involve complete loss of almost all mental functions.

Pick’s disease is known especially for the aphasia it causes. This can distinguish it from other types of frontotemporal dementia, in which behavior problems and personality changes are often a primary first symptom. That said, Pick’s disease can also be associated with behavior problems. Determining with certainty whether a patient has Pick’s disease, another type of frontal lobe dementia, or an altogether different cause of aphasia, is not always possible.

Source : alzheimers.net

It shares some of the characteristics of Alzheimer's diseaseplugin-autotooltip__plain plugin-autotooltip_bigAlzheimer's disease

"Alzheimer’s disease is a chronic progressive neuro-degenerative disorder characterised by three primary groups of symptoms. The first group (cognitive dysfunction) includes memory loss, language difficulties, and executive dysfunction (that is, loss of higher level planning and intellectual coordination skills). The second group comprises psychiatric symptoms and behavioural disturbances — for example, depression, hallucinations, delusions, agitation — collectively termed … - including the build-up of abnormal 'tau proteins' in brain tissue - but, unlike Alzheimer's, the early stages don't tend to feature any memory loss.

Despite more than a century of research, the cause(s) of Pick's disease remains unknown - though genetic and environmental factors are thought likely to be involved. At present. it's mostly considered untreatable.

Further info : Penn Medicine