The patient’s – a psychotic subject – delusion that a close relative or friend has been replaced by an impostor, an exact double, despite recognition of familiarity in appearance and behaviour. The «impostor» is a key figure for the patient at time of onset of symptoms; if married, always the husband or wife accordingly. The patient may also see himself as his own double. As a variant of this syndrome the patient believes that inanimate objects, such as furniture, a letter, a watch, spectacles, have been replaced by an exact double. The syndrome typically accompanies other functional psychoses (such as schizophrenia or affective disorders), although it tends to be the dominating feature. It is also seen in concert with some organic disorders, where it is characterized by more confusion about the misidentification.
Occurs particularly in schizophrenic diseased conditions (paranoid-hallucinatory schizophrenia), but also in affective and organic-psychic disturbances. Both sexes, but prevalent in women. Aetiology unknown.
According to one author, the same condition was described as early as 1893.
- Jack (originally Walter Braden) Finney (1911-1995):
The Body Snatchers. 1955. 2nd edition as The Invasion of the Body Snatchers.
- Fyodor Dostoyevsky:
The Possessed. 1871.
- J. M. J. Capgras, Jean Reboul-Lachaux:
L'illusion des "sosies" dans un délire systématisé chronique.
Bulletin de la Société clinique de médecine mentale, 1923, 11: 6-16.