C9orf72 and frontotemporal dementia: Of note, we also found lower levels of some sphingomyelin species, including SM(d34:1), SM(d38:0), and SM(d40:2), in FTD‐C9orf72, FTD‐GRN, and FTD‐MAPT, respectively, suggesting more broadly de‐regulated sphingolipid metabolism.