Mirrored-self misidentification syndrome in a patient with dementia

ABSTRACT Mirrored-self misidentification, or mirror misidentification syndrome, is a rare but distressing delusional misidentification syndrome (DMS) observed in neurodegenerative conditions, particularly in patients with right hemisphere dysfunction. It can significantly impair caregiver relationships and worsen patient distress. We report a case of a 72-year-old man with mixed dementia who presented with progressive memory loss, followed by gradual-onset mirror misidentification delusions. He developed a delusion of infidelity toward his wife after failing to recognize his mirror image, believing that another man was being cared for preferentially. His condition worsened with a trial of low-dose risperidone due to severe extrapyramidal symptoms. Subsequent treatment with pimavanserin, lemborexant, and memantine, alongside nonpharmacological strategies, resulted in gradual improvement in delusional thinking and stabilization of cognitive symptoms. This case highlights the diagnostic and therapeutic complexity of DMS in dementia. Recognition of mirror misidentification and tailored management – including nondopaminergic antipsychotics and environmental adjustments – can reduce distress and improve outcomes.