Of FTD cases 60% present sporadically (although it is important to bear in mind the possibility of gene mutations in individuals with cryptic family histories).16 The remainder show an autosomal dominant pattern of inheritance, of which 60% are caused by mutations in MAPT, C9orf72 and GRN. 17 In recent years, mutations in particular genes, including MAPT and C9orf72, have been correlated with tau and TDP-43 proteinopathies, respectively. The gene discussed is C9orf72; the disease is frontotemporal dementia.