Frontotemporal lobar degeneration (FTLD) is the second most frequent cause of dementia and is a clinically diverse syndrome, with phenotypes including behavioral changes, semantic dementia and progressive non-fluent aphasia, and characterized by cellular inclusions containing tau (FTLD-tau), TAR DNA-binding protein 43 (TDP-43: FTLD-TDP) or fused-in-sarcoma (FUS: FTLD-FUS) [25, 28]. The gene discussed is MAPT; the disease is semantic dementia.