Dissociation of amyloid biomarkers in PET and CSF in Alzheimer's disease: a case report.

BACKGROUND: Recently, biomarkers have been suggested to be incorporated into diagnostic criteria for Alzheimer's disease (AD). Regarding disease-specific brain amyloid-beta deposition these comprise low amyloid-beta 1-42 in cerebrospinal fluid (CSF) and positive positron emission tomography (PET) amyloid imaging, while neuronal degeneration is evidenced by high total and phosphorylated tau levels in CSF (t-/p-tau), regional hypometabolism ([(18)F]fluorodeoxyglucose PET, FDG-PET) and characteristic atrophy-patterns (magnetic resonance imaging, MRI). CASE PRESENTATION: Here we present a case of clinically and biomarker supported AD (CSF t-/p-tau, MRI, FDG-PET) in a 59-year-old Caucasian man in whom indicators of amyloid-beta deposition dissociated between CSF parameters and the respective PET imaging. CONCLUSIONS: Such cases highlight the necessity to better understand potential dissociations between PET and CSF data for amyloid-beta biomarkers, because they are currently considered interchangeably valid with regard to in-vivo evidence for AD pathology. This is more important since amyloid deposition markers can be considered a very first prognostic indicator of imminent AD, prior to neurodegenerative biomarkers and cognitive symptoms. The case illustrates the need for further longitudinal data on potential dissociations of AD biomarkers to devise recommendations for their better prognostic and diagnostic interpretation in the future.