Delusional Misidentification Syndrome

Delusional Misidentification Syndrome

By Lauren Dubose

This syndrome is usually considered to include four main variants:

• The Capgras delusion is the belief that (usually) a close relative or spouse has been replaced by an identical-looking impostor.
• The Fregoli delusion is the belief that various people the believer meets are actually the same person in disguise.
• Intermetamorphosis is the belief that people in the environment swap identities with each other while maintaining the same appearance.
• Subjective doubles, in which a person believes there is a doppelgänger or double of him or herself carrying out independent actions.

Usually manifesting as symptoms of an underlying disorder (e.g., schizophrenia, mood disorder, delusional disorder, organic disorder), these syndromes rarely occur in isolation.

The Capgras delusion is named after Joseph Capgras (1873–1950), a French psychiatrist who first described the disorder in 1923 in his paper co-authored by Reboul-Lachaux, on the case of a French woman who complained that corresponding "doubles" had taken the places of her husband and other people she knew. This breakdown of communication might be happening between the part of the brain that processes the visual information for faces and the part that controls the limbic system's emotional response.Many researchers think that Capgras syndrome is actually the result of something wrong with the brain.

Some studies have also shown blind people with Capgras syndrome -- their delusion extends to the voice of a person, thinking that the voice is a voice of an impostor, instead of the face, so perhaps it isn't a face-processing problem at all.

Fregoli Delusion

The condition is named after the Italian actor Leopoldo Fregoli, who was renowned for his ability to make quick changes in his appearance during his stage acts. It was first reported in a paper by Courbon and Fail in 1927. They discussed the case of a 27-year-old woman who believed she was being persecuted by two actors whom she often went to see at the theatre. She believed that these people “pursued her closely, taking the form of people she knows or meets.

Case Study

Ms. C., a 58-year-old woman, was brought to our psychiatric emergency room after she called the police and reported there was a stranger in her house. Ms. C. had a history of prior psychiatric hospitalizations and was previously diagnosed with schizophrenia (paranoid type). When the police arrived, she explained that her husband was not her husband but was a stranger. She became argumentative and combative toward the police officers. Due to her history of past psychiatric incidents involving the police, she was brought to the psychiatric emergency room. At the time of the incident, she was known to have consumed half a pint of brandy, and some of her symptoms were thought to be alcohol-related. When evaluated in the emergency room, she reported her distress was due to the impostor that had recently been substituted for her husband and that this impostor made her life miserable. She reported that she could not “take it anymore” and wanted to “get rid of him,” so she called the police. She exhibited paranoid beliefs, such as the neighbors poisoning her, and reported auditory hallucinations. Her medical history and family history were non-contributory. She worked as a housekeeper but quit six months previously because she thought her employer was conspiring against her. On admission to the hospital, Ms. C. presented as well groomed with a somewhat agitated mood and labile affect, expressing paranoid ideation (“A woman down the street steals my belongings and substitutes it with old stuff.”) and experiencing persecutory auditory hallucinations.

After admission, she was started on risperidone 2mg/day. Her paranoid symptoms improved. Her delusions of her husband being substituted by an impostor, however, persisted and did not appear to be related to her alcohol problems. While in the psychiatric unit, she also accused her attending physician of being substituted by an impostor. She was released after three weeks in the hospital with clinical improvement in psychotic symptoms, but the delusion that her husband was an imposter did not improve.

Her psychiatric status and present treatment involvement, if any, are unknown at the time of this writing.

Treatment and prognosis for delusional misidentification syndromes as a result of neurological damage vary widely. In some case studies, the patients recovered slowly over time . In other cases, especially in those of elderly patients, the delusions may continue or become worse, progressing into general dementia. Patients responded with varying success to an array of treatments, including: cognitive and behavioral therapies, electro-convulsive therapy, and the use of pharmaceuticals, such as anti-psychotics, anti-convulsants, neuroleptics, sedatives, and tranquilizers. Unfortunately, treatment effectiveness seems to be as unpredictable as recovery success.

The prevalence is estimated at 0.025-0.03%, lower than the rates for schizophrenia (1%). Delusional disorder may account for 1–2% of admissions to inpatient psychiatric hospitals. Age at onset ranges from 18–90 years, with a mean age of 40 years. More females than males (overall) suffer from delusional disorder, especially the late onset form that is observed in the elderly.

Delusional Misidentification Syndromes is an umbrella term, introduced by Christodouloufor a group of delusional disorders that occur in the context of mental or neurological illness. They all involve a belief that the identity of a person, object or place has somehow changed or has been altered. As these delusions typically only concern one particular topic they also fall under the category called monothematic delusions.