Introduction Delusional misidentification syndrome (DMS) is where a patient reduplicates or incorrectly identifies persons, places, objects or events due to false beliefs. DMS owning to brain lesions are heterogenous in locations, although it has been shown to be more commonly associated with lesions in the right frontal lobe areas. We describe a patient with basal forebrain lesion resulting in amnesia compounded with features of delusional misidentification and specific impairments in emotional perception.

Case Report A 68-year-old man had undergone pituitary surgery for cyst removal, and had developed basal forebrain bleed postoperatively. Four month after, family members noted significant impairments in cognition, including delusional misidentification of his daughter and his house (feeling that his daughter is not his daughter and the house is not his house). Neurobehavioral examination showed Mini Mental State Exam score of 18/30, impaired visual and verbal memory, and executive function.

Comprehensive Affect Testing System (CATS) showed impaired emotional affect perception.

Discussion Basal forebrain lesion typically produced amnestis syndrome. While DMS typically seen in right hemispheric or bifrontal lesion, its description in basal forebrain is uncommon. In this case, we demonstrated DMS from a basal forebrain lesion likely results from mismatch between factual retrieval and emotional processing, as basal forebrain lesion typically affects the neuroanatomy that processes and regulates memory, executive functions, and emotions. This case highlights the importance recognizing DMS in basal forebrain lesion and reaffirms the brain-behavior correlation underpinning DMS phenomenon.