Delusional misidentification syndrome is an umbrella term, introduced by Christodoulou (in his book ''The Delusional Misidentification Syndromes'', Karger, Basel, 1986) for a group of

delusion A delusion is a false fixed belief that is not amenable to change in light of conflicting evidence. As a pathology, it is distinct from a belief based on false or incomplete information, confabulation, dogma, illusion, hallucination, or som ...

al disorders that occur in the context of mental and

neurological illness A neurological disorder is any disorder of the nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord or other nerves can result in a range of symptoms. Examples of symptoms include paralysis, muscle weak ...

. They all involve a belief that the identity of a person, object, or place has somehow changed or has been altered. As these delusions typically only concern one particular topic, they also fall under the category called

monothematic delusion A monothematic delusion is a delusional state that concerns only one particular topic. This is contrasted by what is sometimes called ''multi-thematic'' or ''polythematic'' delusions where the person has a range of delusions (typically the case of ...

s. This psychopathological syndrome is usually considered to include four main variants: * The

Capgras delusion Capgras delusion or Capgras syndrome is a psychiatric disorder in which a person holds a delusion that a friend, spouse, parent, or other close family member (or pet) has been replaced by an identical impostor. It is named after Joseph Capgras (1 ...

is the belief that (usually) a close relative or spouse has been replaced by an identical-looking

impostor An impostor (also spelled imposter) is a person who pretends to be somebody else, often through means of disguise. Their objective is usually to try to gain financial or social advantages through social engineering, but also often for purposes ...

. * The

Fregoli delusion The Fregoli delusion is a rare disorder in which a person holds a delusional belief that different people are in fact a single person who changes appearance or is in disguise. The syndrome may be related to a brain lesion and is often of a parano ...

is the belief that various people the believer meets are actually the same person in disguise. *

Intermetamorphosis Intermetamorphosis is a delusional misidentification syndrome, related to agnosia. The main symptoms consist of patients believing that they can see others change into someone else in both external appearance and internal personality. The disorder ...

is the belief that an individual has the ability to take the form of another person in both external appearance and internal personality. * Subjective doubles, described by Christodoulou in 1978 (''American Journal of Psychiatry'' 135, 249, 1978), is the belief that there is a

doppelgänger A doppelgänger (), a compound noun formed by combining the two nouns (double) and (walker or goer) (), doppelgaenger or doppelganger is a biologically unrelated look-alike, or a double, of a living person. In fiction and mythology, a doppelg ...

or double of themselves carrying out independent actions. However, similar delusional beliefs, often singularly or more rarely reported, are sometimes also considered to be part of the delusional misidentification syndrome. For example: * Mirrored-self misidentification is the belief that one's reflection in a mirror is some other person. * Reduplicative paramnesia is the belief that a familiar person, place, object, or body part has been duplicated. For example, a person may believe that they are in fact not in the hospital to which they were admitted, but an identical-looking hospital in a different part of the country, despite this being obviously false. * Cotard's syndrome is a rare disorder in which people hold a

al belief that they are

dead Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

(either figuratively or literally), do not exist, are

putrefying Putrefaction is the fifth stage of death, following pallor mortis, algor mortis, rigor mortis, and livor mortis. This process references the breaking down of a body of an animal, such as a human, post-mortem. In broad terms, it can be view ...

, or have lost their

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

internal organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...

. In rare instances, it can include delusions of immortality. * Syndrome of delusional companions is the belief that objects (such as soft toys) are sentient beings. * Clonal pluralization of the self, where a person believes there are multiple copies of themselves, identical both physically and psychologically, but physically separate and distinct. *

Clinical lycanthropy Clinical lycanthropy is a rare psychiatric syndrome that involves a delusion that the affected person can transform into, has transformed into, or is, an animal. Its name is associated with the mythical condition of lycanthropy, a supernatural ...

is the belief that one is turning or has turned into an animal. It is considered a delusional misidentification of the self. There is considerable evidence that disorders such as the Capgras or Fregoli syndromes are associated with disorders of

face perception Facial perception is an individual's understanding and interpretation of the face. Here, perception implies the presence of consciousness and hence excludes automated facial recognition systems. Although facial recognition is found in other sp ...

and recognition. However, it has been suggested that all misidentification problems exist on a continuum of anomalies of familiarity, from

déjà vu ''Déjà vu'' ( , ; "already seen") is a French loanword for the phenomenon of feeling as though one has lived through the present situation before.Schnider, Armin. (2008). ''The Confabulating Mind: How the Brain Creates Reality''. Oxford Univers ...

at one end to the formation of delusional beliefs at the other.

References

{{Delusion Psychosis Delusional disorders Psychopathological syndromes Delusions

See also

References