Introduction: Functional neurological symptom disorder (FNSD) is a common diagnosis among adolescents. However, we feel it is a difficult diagnosis to assess because of the diversity of its clinical manifestations, the rapid changes in its nosography over the years, and its common imbrication with established somatic diagnoses. We would like to illustrate this hypothesis through a case presentation and the original diagnostic process that emerged from it. Methods: We chose to present our diagnosis approach through the case of an 11-year-old boy who showed a progressive loss of motor and sensory function to the point of total dependency, and then suddenly switched between this state and a “normal” physical presentation, while deliriously claiming to be an angel. Results: All possible infectious, autoimmune, metabolic, and toxic disorders were ruled out. After the successive therapeutic failures of antidepressants and neuroleptics, FNSD was diagnosed. Conclusion: The DSM-5-TR classification was insufficient to explain the full clinical picture and a complementary approach (biblical, psychoanalytical, and historical) was used to analyze the cause of this atypical presentation.