The most common causes of FTD are mutations in the genes that encode C9orf72, tau (MAPT) and progranulin (GRN), with less common causes identified as mutations in valosin-containing protein, TDP-43 (TARDBP), fused in sarcoma and charged multivesicular body protein 2B (CHMP2B) (3). The gene discussed is C9orf72; the disease is frontotemporal dementia.