Preventing violence in schizophrenia: Why do delusional familiarity disorders remain so unfamiliar?

To the Editor

Delusional misidentification syndromes (DMSs) are psychopathological phenomena that carry the delusional belief of misidentification of familiar persons or objects and the conviction that they have been replaced or transformed. They occur in a variety of medical conditions but appear to be strongly associated with schizophrenia (Lykouras et al., 2008). Although DMS clinically appear underdiagnosed, their true prevalence in all psychiatric inpatients ranges from 1.3% to 4.1% (Klein and Hirachan, 2014).

While there is still a paucity of literature on DMS (Klein and Hirachan, 2014), several authors have reported the risk of dangerousness in patients with DMS and recommended a systematic screening of misidentification syndromes in assessments of the degree of dangerousness of psychotic individuals (Klein and Hirachan, 2014; Silva et al., 1992). Here, we present a case of a patient who developed a DMS which led him to kill the delusional misidentified person.

Mr T. is a 28-year-old man with an 8-year history of DSM-5-defined paranoid schizophrenia and five hospital admissions for acute psychotic episodes following treatment interruption. Significant clinical improvement was systematically observed after the re-introduction of antipsychotic treatment.

Mr T. killed his neighbour. The homicide took place in the stairwell; Mr T. severely struck his neighbour with dumbbells and eventually murdered him. He had no prior criminal history. About 1 year before the killing, Mr T. once more discontinued his treatment.

Mr T. was incarcerated and rapidly transferred to a hospitalization unit for inmate patients because of delusions of persecution and disorganized thought processes. During the hospitalization, he explained that on the day of the homicide, he met his neighbour and realized that this person was an impostor. He was unable to pinpoint the differences between the impostor and his neighbour, but he was convinced that his real neighbour had been killed by the impostor who should be eliminated.

The psychopathology of Mr T. is consistent with Capgras syndrome – a typical case of DMS. In line with previous studies (Klein and Hirachan, 2014), this syndrome was found to favourably respond to antipsychotics. We would like to draw attention to these familiarity disorders because of their forensic consequences and the possible treatment approaches. We think that a greater consideration for these disorders could help to prevent some acts of violence in delusional patients, and it may ultimately contribute to an improvement in the therapeutic care of such patients.