Capgras Syndrome The patient believes that someone else has replaced a familiar person. Both have a close resemblance. For example, an unknown person replaces the daughter. The patient may attack the familiar person. The original name was ‘delusion des sosies’ a delusion and not a syndrome an example of reduplicative paramnesia.. the most common cause is schizophrenia. other causes include Lewy body dementia and other neuropsychiatric disorders. Always assess the risk of violence to the family person.