Amyloid-PET Positive Patient with bvFTD: Wrong Diagnosis, False Positive Scan, or Co-pathology?

A 65-year-old man was referred to a local memory clinic with memory complaints but clinical assessment found no abnormalities. When he presented two years later to our clinic social disinhibition, reduced empathy, poor judgment and hoarding had become obvious. He showed no insight. He had ischemic heart disease and was on preventive treatment. His mother died aged 97 suffering from dementia. Neurological examination was normal. During neuropsychological examination he exhibited verbal and behavioral disinhibition, inattention, emotional blunting and unconcern. He had prominent difficulties in abstraction, set shifting and sequencing with significant impact on memory tests (table1). A clinical diagnosis of behavioral variant FTD (bvFTD) was made. MRI (figure A) showed right more than left-sided temporal atrophy, bilateral frontal and milder parietal atrophy. Fluorodeoxyglucose (FDG)-PET (figure B) demonstrated fronto-temporal hypometabolism. Metabolism in the posterior cingulate was normal. He was homozygous for the APOE ε4 allele and negative for the C9orf72 expansion and mutations in MAPT, GRN, PSEN1, and APP. [18F]-Florbetapir PET (figure C) revealed increased tracer binding in all cortical regions corresponding to a centiloid value of 74%.