Capgras syndrome is a delusion in which the patient believes that a particular individual has been replaced by an imposter. It is observed in patients with psychiatric disorders such as schizophrenia but also occurs in patients with a neurodegenerative disease including Lewy body disease and Alzheimer’s disease. Here we report a patient with early-onset Alzheimer’s disease who presented with a unique form of Capgras syndrome.

An early 60’s right-handed woman with 12 years of education, visited our outpatient clinic for evaluation of her memory impairment. Neurological examination was not remarkable. A MMSE score was 25/30 and a neuropsychological examination indicated mild impairment of attention and episodic memory, and relatively preserved visuospatial function. Six months after the initial visit of our clinic, she started to claim that she met several imposters of her husband. She called each imposter in different name, described each as a slightly different appearance, and expressed different level of sense of familiarity. An additional examination of face recognition using photographs of her husband revealed that there was a difficult to recognize her husband especially viewed from the side of his face. In addition, she showed a difficulty in discriminating between two different unknown faces and in judging approximate age of face in photographs. Brain MRI showed no significant atrophy and IMP-SPECT showed an extensive hypoperfusion in the bilateral, right-side dominant temporal, parietal, and occipital lobes. Both FP-CIT SPECT and MIBG scintigraphy were negative. Florbetapir PET was positive. Thus, a diagnosis of early-onset Alzheimer's disease was made. Acetylcholinesterase inhibitors and antipsychotics were used to treat her Capgras syndrome, but the symptom lasted for more than a year.

There are several possible factors that may induced patient’s unique Capgras syndrome: (1) psychodynamic background- the patient and her husband had been in a long-term common-law relationship; (2) mild impairment in face recognition; (3) dysfunction of right hemisphere, which is known to be strongly related to Capgras syndrome. The combination of these factors may result in the occurrence of multiple imposters of her husband with different degrees of familiarity.