Background: The syndrome of folie a deux is uncommon and often described in the context of schizophrenia. We report a case of induced delusional disorder associated with bipolar affective disorder (BAD).
Case report: We present a case of monozygotic twins in their late 60s with an unusually close relation with one another and relative isolation from other people. Both twins have been diagnosed as suffering from BAD and relapsed into mania with psychotic symptoms. During their hospital stay they exhibited features consistent with folie a deux. Separation caused disappearance of the phenomenon whilst the affective disorder persisted.
Conclusion: This case highlights the unusual and rare phenomenon of folie a deux occurring in the context of BAD. It also suggests current difficulty in defining folie a deux as an entity according to current diagnostic criteria.