[Folie à deux].

Folie à deux or induced psychotic disorder is a rare psychiatric illness. The essential feature is a psychotic disorder shared by two emotionally close persons, usually close relatives. The disorder is characterized by a primary psychotic person who gradually imposes her delusional beliefs on the other person. The disorder usually resolves in the more passive person when the two are separated (e.g. by admittance of the primary psychotic person). This case report describes a shared delusional belief between two friends.