It is estimated that these three genes are responsible for approximately half of familial FTD cases and approximately 10–30% of all FTD cases, whereas the remainder is considered sporadic.2 FTLD is pathologically associated primarily with either misfolded transactive response (TAR) DNA-binding protein 43 (TDP43) or misfolded tau protein aggregates in neurons. The gene discussed is MAPT; the disease is frontotemporal dementia.