The<unk>  (or<unk> 's syndrome) is a rare disorder in which a person holds a delusional belief that an acquaintance, usually a spouse or other close family member, has been replaced by an identical looking impostor. The<unk>  is classed as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places or objects. It can occur in acute, transient, or chronic forms.
The delusion is most common in patients diagnosed with schizophrenia, although it can occur in a number of conditions including after brain injury and dementia. Although the<unk>  is commonly called a syndrome, because it can occur as part of, or alongside, various other disorders and conditions, some researchers have argued that it should be considered as a symptom, rather than a syndrome or classification in its own right.
Capgras delusion
Cotard delusion
Fregoli delusion
Monothematic delusion
Homicidal ideation
Schizotypy
Suicidal ideation
Malignant narcissism