To purpose of this case presentation is to identify the different delusional syndromes based on localization of brain lesion. 

Delusional beliefs fall under the category of delusional misidentification syndromes (DMS’s). Both Capgras and Fregoli’s delusions (FDs) are associated with facial recognition, perception, and processing problems. Capgras and FD delusions can be associated with right hemisphere lesions. 

We present a case of a 66-year-old male who has come to the hospital with persistent altered mental status for the last two weeks. The patient was alert but not oriented to place or time. Urine drug screen and metabolic profile were normal. He had a pressured speech and immediately greeted the physician by the name of a law enforcement official from his hometown (“Hey there Mr. P!). We tried to correct him, and he did not disagree but later in the interview called again with the same “Mr. P” name multiple times. He believed that there were multiple individuals including family members who had assaulted him to take his money or belongings. He also expressed safety concerns with the people around despite multiple re-assurances. The circumstantial thought process with sub-acute presentation prompted a magnetic resonance imaging (MRI) brain which demonstrated the right temporal lobe mass with edema and multiple solid lesions suggestive of metastatic from non-small cell lung carcinoma (NSCLC). Although, positron emission tomography (PET) scan was negative a month ago. Patient's behavior improved with Olanzapine 10 mg twice a day and Dexamethasone followed by chemo-radiotherapy for brain lesions.

We conclude that the persecutory delusions and FDs can lead to concerning symptoms such as refusing any oral intake, combativeness, and discomfort. Fregoli delusion in association with temporal lobe mass is not very common but when suspected from patient interviewing, one should screen with neuroimaging.