[Folie à deux, symptoms sharing us a relationship modality: a case report].

Shared Psychotic Disorder or Folie à deux is a rare and controversial entity that raises phenomenological, nosographic and psychopathological issues. It questions the nature of dilusion and its occurrence outside the psychotic structure and also the issue of symptoms contagion in psychiatry. We offer a semiological analysis of an intrafamilial case of Folie à deux, a case with the clinical specificity of sharing not only delusional symptoms but also non-delusional psychotic elements. We then dig back in the epidemiological characteristics and common factors to other reported cases in the literature of different cultures. Then we draw a history of the entity and its evolution over the classifications since its first description by Legrand to the DSM 5. From here, we emphasize the insufficiency of a purely descriptive approach and focus on the possible link with other more common clinical situations of mental symptoms transmission between two or more persons. Then, we propose a psychopathological reflection that essentially targets the sharing of the symptom rather than its nature while questioning the function of the delusion in a delusional couple.