Shared psychotic disorder between a girl with her mother and younger sister (folie a trois).

Shared psychotic disorder develops in an individual in the context of a close relationship with another one who has an established delusion that he/she also believes. It is classified within paranoid disorder. Herein, we present a case of two sisters with their mother. The elder sister was the origin of paranoid delusion. Her delusion was with a dentist who tries his best to prevent her for marrying. They separated completely from all their relatives for two years.