Delusional sharing: a history focus-on and case report of folie à deux.

Folie à deux (FAD) is a clinical condition that was first described by Lasègue and Falret in 19th century. They reported a rare condition where two or more people shared delusional ideas from a person to another. Nowadays a trace of this historical diagnosis and its theoretical framework, could be found on ICD-10 where FAD is translated in “Shared Psychotic Disorder”. Given the lack of literature and a well-defined set of symptoms it is hard to detect the clinical limits of FAD. Furthermore, the complex of comorbidities could lead to a misdiagnosis. In this paper we report a peculiar case of FAD with an historical focus trying to give a wider point of view and tools to recognize this unconventional psychiatric diagnosis.