Pseudologia Fantastica (PF) is an understudied and poorly understood entity, first described by a German psychiatrist in the late 19th century. The terms mythomania and pathological lying are often used interchangeably.

In addition to reviewing the literature around PF and its place nowadays in the current diagnostic system, we report the case of an adolescent female who suffered from PF.

We describe and analyse a clinical case of PF and make a bibliographic review about this disorder.

Typically, PF has its onset during adolescence and the clinical picture is often very uniform. The central features include a marked tendency to lie that is both quantitatively and qualitatively quite distinct from “normal” lying. Instead of being a goal-directed lie, pseudology lacks an obvious motive and is often more associated with internal motives, which can constitute some kind of gratification on their own.

The only diagnosis available in our current diagnosis system that accounts for prominent purposeless deception is the Axis I Factious Disorder diagnosis. Despite this, some Personality Disorders should always be considered as possible comorbidity of PF.

While cases of PF are thought to be quite rare overall, they have been documented all over the world. There is the need for further case studies and reviews to be published on this issue in order to determine whether PF should be better understood on Axis I or Axis II of our diagnostic system. Greater awareness of its medical, social and legal consequences is mandatory.