A previous study in C9orf72 mutation carriers with FTD, FTD-ALS, and ALS clinical phenotypes identified that an increase in DNAm age acceleration was associated with an earlier age of onset and shorter disease duration in the blood, but with just earlier onset in the frontal cortex and spinal cord tissue, thus reflecting the severity/progression of the disease [18]. Here, C9orf72 is linked to amyotrophic lateral sclerosis.