[The 'signe du miroir'. Psychopathological reflections on a forgotten phenomenon]

At the beginning of the last century, the 'signe du miroir' was considered to be a frequent and alarming prodrome of schizophrenia. Since then, the concept has fallen into oblivion.

To study and clarify the 'signe du miroir' concept in an attempt to bridge the gap between observable behaviour and subjective experiences.

Background information was obtained by searching on PubMed, Google Scholar and Google and applying the snowball method.

In various psychiatric disorders, patients may experience disturbing disorders of self-perception. By seeing themselves in a mirror they are able to test their experiences against external reality. Presumably this is the phenomenon that underlies the 'signe du miroir'. In theory, this phenomenon may mark the transition from intact reality testing to aberrant reality testing. In practice, talking about the phenomenon may lead to more comprehensive and earlier diagnosis of psychopathology and to a better working relationship.

A forgotten phenomenon such as the 'signe du miroir' illustrates the value of reinstating the practice of observing patients meticulously and thereby developing the ability to perceive patients underlying subjective experiences.