More recently, Tarr and coworkers (2019) analyzed the blood methylome and transcriptome of a longitudinal ALS-discordant cohort comprising monozygotic triplets and twins and representing the three most common types of ALS, namely C9orf72-linked ALS, SOD1-linked ALS, and sporadic ALS. Here, C9orf72 is linked to amyotrophic lateral sclerosis.