Delusional misidentification syndrome

Overview

Delusional Misidentification Syndrome (DMS) is a group of rare psychiatric disorders characterized by a persistent belief that people, places, or objects have been replaced, transformed, or duplicated. Despite clear evidence to the contrary, individuals with DMS are convinced of the altered identity of familiar entities. These syndromes are often associated with psychosis, neurodegenerative diseases, or brain injury. The most well-known types of DMS include Capgras syndrome, Fregoli syndrome, intermetamorphosis, and subjective doubles.

Causes

DMS is believed to result from a disruption in the brain’s recognition and emotional response systems, particularly in areas involved with face perception, memory, and reality testing. Underlying causes may include:

• Psychiatric disorders: Schizophrenia, schizoaffective disorder, bipolar disorder with psychotic features.

• Neurological conditions: Alzheimer's disease, dementia, Parkinson’s disease, epilepsy, or stroke.

• Brain trauma: Traumatic brain injury, especially involving the right hemisphere or frontal/temporal lobes.

• Substance use: Drug-induced psychosis or intoxication.

• Disconnection syndromes: Impaired linkage between visual recognition areas (e.g., fusiform gyrus) and the limbic system, which regulates emotional response.

Symptoms

The hallmark symptom of DMS is a fixed false belief related to identity misrecognition. The specific symptoms depend on the subtype:

• Capgras syndrome: Belief that a close relative or friend has been replaced by an identical impostor.

• Fregoli syndrome: Belief that different people are actually a single person who changes appearance or is in disguise.

• Intermetamorphosis: Belief that people have physically and psychologically transformed into someone else.

• Subjective doubles: Belief in the existence of a duplicate of oneself acting independently.

Additional features may include paranoia, hallucinations, hostility toward the “impostor,” and difficulties in social or occupational functioning.

Diagnosis

Diagnosing DMS involves a comprehensive psychiatric and neurological evaluation. Steps include:

• Clinical interview: Detailed assessment of delusional content, onset, and coexisting symptoms.

• Mental status examination: Evaluation of cognition, perception, mood, and thought processes.

• Neuroimaging: MRI or CT scans may reveal structural brain abnormalities or lesions in regions involved in recognition and emotion processing.

• Neuropsychological testing: Assessment of memory, executive function, and visual processing to identify cognitive deficits.

• Differential diagnosis: Excluding other causes of psychosis, such as delirium, substance abuse, or neurological disease.

Treatment

Treatment of Delusional Misidentification Syndrome is tailored to the underlying cause and symptom severity. Management strategies include:

• Antipsychotic medications: Atypical antipsychotics like risperidone, olanzapine, or aripiprazole are commonly used to reduce delusional thinking.

• Mood stabilizers: Used if the delusions are part of a mood disorder such as bipolar disorder.

• Cognitive Behavioral Therapy (CBT): Helps patients challenge delusional beliefs and improve reality testing.

• Supportive psychotherapy: Focuses on improving coping strategies and maintaining social relationships.

• Treatment of neurological causes: Addressing underlying dementia, brain injury, or epilepsy may reduce symptoms.

• Hospitalization: May be necessary in severe cases, particularly if there’s a risk of harm to self or others.

Prognosis

The prognosis for Delusional Misidentification Syndrome varies based on the underlying cause, duration of symptoms, and responsiveness to treatment. In psychiatric cases (e.g., schizophrenia), symptoms may improve with medication and therapy, although relapse is possible. Prognosis tends to be poorer when DMS is linked to neurodegenerative diseases like Alzheimer’s, where cognitive decline is progressive. Early diagnosis, integrated treatment, and supportive care significantly improve outcomes and reduce distress associated with the condition.