For example, while the clinical phenotype of three causative genes for FTD, C9orf72, MAPT and GRN, are associated with a similar behavioral variant FTD (bvFTD) presentation, the underlying protein pathology varies such that MAPT mutations are associated with tau pathology and C9orf72 and GRN mutations are associated with Tar-DNA-binding protein (TDP)-43 pathology [3]. The gene discussed is C9orf72; the disease is frontotemporal dementia.