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 interchange, and they display the common concept of the double (sosie).
[1] They all involve a belief that the identity of a person, object, or place has somehow changed or has been altered.
[3] This psychopathological syndrome is usually considered to include four main variants:[4][2] However, similar delusional beliefs, often singularly or more rarely reported, are sometimes also considered to be part of the delusional misidentification syndrome.
However, it has been suggested that all misidentification problems exist on a continuum of anomalies of familiarity,[13] from déjà vu at one end to the formation of delusional beliefs at the other.