GPNMB protein levels were quantified with sandwich ELISAs in CSF samples from individuals that were cognitively normal (controls; n = 14) and individuals with known mutations that cause FTD (FTD-GRN n = 13, FTD-C9orf72 n = 13, or FTD-MAPT n = 12). The gene discussed is C9orf72; the disease is frontotemporal dementia.