DNAm age was repeatedly reported to be higher in individuals with ALS in comparison with their monozygotic twin, or triplets [70,71,72], not only in sALS cases [70,71], but also in SOD1-ALS [71,72] and C9-ALS cases [71], indicating that DNAm might strongly influence the penetrance of a causative mutation. The gene discussed is C9; the disease is amyotrophic lateral sclerosis.