Delusional misidentification syndrome

Delusional misidentification syndrome is an umbrella term, introduced by Christodoulou (in his book The Delusional Misidentification Syndromes, Karger, Basel, 1986) for a group of four delusional disorders that occur in the context of mental and neurological illness. They are grouped together as they often occur simultaneously or interchangeably, and they display the common concept of the double (sosie).

Source: Wikipedia — Delusional misidentification syndrome (CC BY-SA 4.0)