[Folie a deux: a nosographic question or just a shared madness?]

Folie a deux was described by Lasègue and Falret in 1877. The concept evolved thus giving rise to different variants of the same reported phenomenon. Taking a clinical case as an example, a review of the nosological definition of shared psychotic disorder was performed. Limitations were found in its descriptions of the subtypes of this unique clinical picture. In this paper we evaluate if its argument has real implications for the purpose of establishing a diagnosis and performing a definite therapeutic approach.