To investigate possible differences in pTDP-43S375 immunoreactivity in the spectrum of TDP-43 pathology in more detail, a cohort of 44 ALS–TDP and FTLD–TDP cases, including FTLD–TDP types A-C and those with GRN and C9orf72 mutations, was examined. Here, C9orf72 is linked to amyotrophic lateral sclerosis.