C9orf72 and frontotemporal dementia: Altered lipid metabolism may not be limited to FTD due to GRN mutations, since elevated ganglioside levels were found across patients with different mutations—e.g., GM3(d18:1_16:0), GM3(d18:1_18:0) in FTD‐C9orf72 and FTD‐MAPT.33