GRN and proteostasis deficiencies: bvFTD is most often caused by frontotemporal lobar degeneration (FTLD) proteinopathies, namely tauopathies (of which microtubule-associated protein tau (MAPT) gene mutations are the most common genetic causes), TDP-43 proteinopathies (of which chromosome 9 open reading frame 72 (C9orf72) and progranulin (GRN) gene mutations, in order of frequency, are most common), and less frequently, fused in sarcoma (FUS) proteinopathies [19].