Tsai et al. [63] examined the tau tracer 18F-flortaucipir in 11 patients with nonfluent variant primary progressive aphasia (nfvPPA), 10 with corticobasal syndrome (CBS), 10 bvFTD subjects, two with svPPA, and six with FTD-associated pathogenic genetic mutations, microtubule-associated protein tau (MAPT), five with chromosome nine open reading frame 72 (C9ORF72) association, and one associated with progranulin (GRN) mutation. This evidence concerns the gene GRN and primary progressive aphasia.