Duplication of amyloid precursor protein (APP), but not prion protein (PRNP) gene is a significant cause of early onset dementia in a large UK series.

"Disclosure statement D. McNaughton, W. Knight, R. Guerreiro, N. Ryan, J. Lowe, M. Poulter, D. Nicholl, J. Hardy, J. Collinge, and S. Mead report no disclosures. T. Revesz has received research grant support from Orion Pharma and had a consulting agreement with Merck Serono. He is supported by the Alzheimer's Research Trust and the Sarah Matheson Trust for Multiple System Atrophy and Brain Net Europe. J. Lowe is affiliated with an Alzheimer's Research Trust center supported by an ART center grant. M. Rossor is an NIHR Senior Investigator and SMC for Wyeth/Elan Bapineuzumab study. All patients gave informed consent for genetic analysis. Ethical approval for the study was given by the University College London Hospitals NHS Trust Local Ethics Committee."

"This work was funded by the UK Medical Research Council. All UCL Institute of Neurology affiliated coauthors received support from the NIHR funded UCL/UCLH Comprehensive Biomedical Research Centre. The Dementia Research Centre is an Alzheimer's Research Trust coordination center. Ray Young assisted with figures. This work was supported in part by the Intramural Research Program of the National Institute on Aging, National Institutes of Health, Department of Health and Human Services, project number Z01 AG000950-06. We thank all patients, their families, carers, and physicians whose histories and assessments have been used in the case reports."