Rare proteinopathies include FTLD-UPS (ubiquitin proteasome system), caused by mutations in chromatin-modifying protein 2B (CHMP2B) [16, 17] and FTLD-FUS (fused in sarcoma) [18], or FTLD with inclusions belonging to other proteins of the FET family (FUS, EWSR1, and TAF15 family of proteins) [19], for which the underlying genetic causes are still unknown. Here, FUS is linked to sarcoma.