The<unk>  or<unk>  syndrome 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 paranoid nature with the delusional person believing that he or she is being persecuted by the person he or she believes to be in disguise.
The condition is named after the Italian actor Leopoldo<unk>  who was renowned for his ability to make quick changes of appearance during his stage act.
It was first reported in a paper by P. Courbon and G. Fail in 1927 (Syndrome d’illusion de<unk>  et schizophrénie). They discussed the case study of a 27-year-old woman who believed she was being persecuted by two actors whom she often went to see at the theatre. She believed that these people "pursued her closely, taking the form of people she knows or meets".
The<unk>  is classed both as a monothematic delusion, since it only encompasses one delusional topic, and as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places or objects. Like Capgras delusion, it is thought to be related to a breakdown in normal face perception.
Fregoli delusion
Cotard delusion
Capgras delusion
Monothematic delusion
Beck's cognitive triad
Schizotypy
Bibliomania
Munchausen syndrome by proxy