Importance of Capgras syndrome in shared psychotic disorder: a case report

Shared psychotic disorder characterized by Capgras syndrome is an extremely rare condition. To our knowledge, there are only a few published papers on this condition. This paper presents a case of shared Capgras syndrome in two sisters. The inducer was a younger sister with schizophrenia, who passed on her Capgras delusion to her older sister after the death of their father. After committing a violent offense caused by Capgras delusion, a court ordered the sisters’ involuntary admission to a psychiatric hospital. After being separated and receiving antipsychotic treatment, the sisters showed substantial improvement. However, shortly after hospital discharge, they stopped taking their medication and disappeared. After 15 years, their mother died and shortly afterwards, the sisters were re-admitted for forensic psychiatric evaluation after another violent crime caused by Capgras delusion. Timely recognition, adequate treatment and maintaining a therapeutic alliance could contribute to a better clinical course and outcome of this disorder, and reduce the risk of violent behavior.