Delusional Misidentification Syndromes: Separate Disorders or Unusual Presentations of Existing DSM-IV Categories?

During the past 80 years, delusional misidentification syndromes (DMS), especially the Fregoli and Capgras syndromes, have posed challenges to mental health professionals due to a lack of comprehensive understanding of the syndromes and a lack of effective treatment. An issue that remains to be unresolved is whether DMS (either in its pure form or as embedded symptoms of other diagnoses) can be accommodated in the present Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). During the past two decades, neurophysiological and neuroimaging studies have pointed to the presence of identifiable brain lesions, especially in the right frontoparietal and adjacent regions, in a considerable proportion of patients with DMS. Prior to the advent of such studies, DMS phenomena were explained predominantly from the psychodynamic point of view. Deficits in working memory due to abnormal brain function, are considered to play causative roles in DMS. In this article, we present two cases of Fregoli and Capgras syndromes and discuss the relevant theoretical and practical issues.