Capgras syndrome in Alzheimer’s disease

Capgras syndrome (CS), also known as the illusion of doubles, is a subtype of delusional misidentification syndromes (DMS), often observed in psychotic manifestations of Alzheimer’s disease (AD). The prevalence of DMS in AD psychosis is estimated to be approximately 30%, with 5% to 16% of DMS cases presenting with CS. The pathophysiology of CS remains unclear; however, one prevailing hypothesis suggests that it may result from disrupted connectivity between brain regions responsible for facial recognition and those involved in emotional processing. Currently, there is no standardized treatment protocol for CS. However, some improvement has been noted with standard AD treatment regimens and validation therapy, which involves acknowledging and verbalizing the patient’s emotions. This paper aims to provide a detailed description of a clinical case and an overview of the pathophysiology of CS. We present the case of an 83-year-old female patient with a medical history significant for major depressive disorder, major neurocognitive disorder, and several comorbid conditions who was referred to our clinic with complaints of memory and attention impairment, temporal disorientation, behavioral disturbances, and delusions. The patient’s medical history revealed a delusional conviction that her daughter had been replaced by an imposter, a belief that persisted during in-person interactions but was absent during telephone conversations. A brain scan (computer tomography [CT]) revealed cerebral and cerebellar atrophy, and the patient’s Mini-Mental State Examination (MMSE) score was 19/30.