Fregoli delusion

# Overview
The Fregoli delusion or Fregoli syndrome is a rare disorder in which a person holds a delusional belief that different people are in fact a single person who changes appearance or is in disguise. The syndrome may be related to a brain lesion and is often of a paranoid nature with the delusional person believing that he or she is being persecuted by the person he or she believes to be in disguise.
The condition is named after the Italian actor Leopoldo Fregoli who was renowned for his ability to make quick changes of appearance during his stage act.
It was first reported in a paper by P. Courbon and G. Fail in 1927 (Syndrome dillusion de Fregoli et schizophrenie). They discussed the case study 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".
The Fregoli delusion is classed both as a monothematic delusion, since it only encompasses one delusional topic, and as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places or objects. Like Capgras delusion, it is thought to be related to a breakdown in normal face perception.

# Symptoms
- Delusions/hallucinations.
- Defeciency of visual memory.
- Self awareness defeciency.
- Executive function defeciency.
- Hindrance of cognitive flexibility.
- Seizures/epileptogenic symptoms.

# Etiology
- Levodopa therapy- It is clinically used to treat Parkinson's disease and dopamine-responsive dystonia. Clinical studies have shown that the use of levodopa can lead to visual hallucinations and delusions. In most patients, delusions were more salient than hallucinations. Over prolonged use of levodopa, the delusions almost occupy all of a patient's attention.  It has been concluded that delusions related to antiparkinsonian medications are one of the leading causes of Fregoli syndrome.
- Traumatic brain injury- Injury to the right frontal and left temporo-parietal areas can cause Fregoli syndrome. It has been seen that significant deficits in executive and memory functions follow shortly after damage in the right frontal or left temporoparietal areas.
- Lesion in Fusiform gyrus- Lesions in the right temporal lobe and the fusiform gyrus may contribute to DMSs. MRIs of patients exemplifying Fregoli symptoms have shown parahippocampal and hippocampal damage in the anterior fusiform gyrus, as well as the middle and inferior of the right temporal gyri. The inferior and medial of the right temporal gyri are the storage locations for long-term memory in retrieving information on visual recognition, specifically of faces; thus, damage to these intricate connections could be one of the leading factors in face misidentification disorders.
- Abnormal P300-  In comparison to normal patients, DMS patients generally exhibit an attenuated amplitude of P300 at many abductions. These patients also exhibit prolonged latencies of P300 at all abductions. These implications suggest that DMSs are accompanied by abnormal WM, specifically affecting the prefrontal cortex (both outside and inside).

# Treatment
Antipsychotic drugs are the frontrunners in treatment for Fregoli and other DMSs. In addition to antipsychotics, anticonvulsants and antidepressants are also prescribed in some treatment courses.