C9orf72 and frontotemporal dementia: The data were filtered by proteins present in at least 50% of samples in one of the six groups (sporadic ALS, C9orf72 ALS, sporadic FTD, C9orf72 FTD, asymptomatic C9orf72 HRE carrier, and asymptomatic non‐carrier), leaving 1,245 for analysis.