Delusional misidentification incident in a right hemisphere stroke patient

We report a delusional misidentification incident lasting some hours in which a man who had suffered a right hemisphere stroke, HW, mistook a student for his daughter. Investigation of HW's face processing abilities showed unimpaired ability to recognize familiar faces and match facial expressions, but severe impairments of unfamiliar face matching both on the Benton test and a task requiring the matching of disguised and undisguised faces. The incident shows some similarity to the Frégoli delusion, which has also been noted following brain injury affecting the right cerebral hemisphere.