The prevalence of misidentification syndromes in neurodegenerative diseases.

Although misidentification syndromes (MISs) have been often described in Alzheimer disease (AD), the prevalence of these phenomena in different neurodegenerative diseases has not been systematically studied. Three hundred ninety-two individuals with probable AD, 119 patients with the behavioral variety of frontotemporal dementia (FTD-bv), 101 patients with primary progressive aphasia, 24 subjects with semantic dementia, 18 subjects with corticobasal degeneration, 8 patients with progressive supranuclear palsy, 36 individuals with probable Lewy body dementia (DLB), and 26 subjects with Parkinson disease (PD) were the participants of this study. On the basis of a semistructured interview with both patients and their reliable caregivers, MIS was identified in 15.8% of cases with AD, 16.6% of patients with DLB, and in 8.3% of individuals with semantic dementia. The most frequent form of MIS was Capgras delusions, often accompanied by reduplication of place, phantom border phenomenon, or both. Although MIS typically appears in later stages of the disease, it can also occur surprisingly early in patients with AD. None of the patients with FTD-bv, primary progressive aphasia, corticobasal degeneration/supranuclear palsy, or PD developed MIS. Thus, our findings suggest that MISs are characteristic of AD and DLB, and tend to exclude FTD/Pick complex and PD.