Paraphrenia is a chronic psychotic disorder with a better-preserved affect and minimal disturbances of emotion and volition and a much less cognitive deterioration and personality changes.

To report a case with probable Paraphrenia and to highlight the importance of the differential diagnosis in a first psychotic episode.

Case report and systematic review of the literature.

We report a case of a 41-year-old man without a past psychiatry history that was led to the psychiatry emergency department (PED), by officers, because of strange behaviour and aggressiveness towards his family. In the PED the patient said that his real father was his father-in-law and that his ex-wife was his sister. His mental exam revealed disinhibition, disorganized speech with slightly mood elation, persecutory, mystic and influential delusions with various delusional interpretations. After being admitted to the psychiatric ward, in compulsatory care, he began treatment and a medical work up was completed. According to the family the patient had begun this strange behaviour four years prior. During the hospitalization it became clear that the patient was experiencing imaginative-confabulatoric multi-thematic delusions, sometimes interviewer guided, without showing cognitive deterioration and retaining his personality.

The diagnosis of atypical psychosis or psychosis not otherwise specified is not satisfactory since it agglutinates different conditions together. Paraphrenia is a well-established concept and should be used in order to define a group of psychotic patients who exhibited characteristic symptoms of schizophrenia, minus personality impairment and slower cognitive decline.

The authors have not supplied their declaration of competing interest.