Other current frequency studies usually exclude subjects in whom a genetic defect has been found before (e.g., C9orf72 expansions, GRN, or MAPT), describe nonconsecutive series based on prior explicit or implicit selection criteria, or study only single genes or a small set of genes, without screening all genes associated with neurodegenerative dementias, and thus do not provide an unbiased, representative estimate of the full genetic landscape of clinical FTD.15, 26, 27. This evidence concerns the gene C9orf72 and frontotemporal dementia.