C9orf72 and amyotrophic lateral sclerosis: In this study, we sought to: (1) identify aberrant miRNAs from circulating exosomes of SOD1-ALS, C9orf72-ALS, and SALS by microarray screening and RT-qPCR validation; (2) construct a support vector machine (SVM) model by using differentially expressed miRNAs between SALS and HCs to help diagnose ALS; and (3) perform functional analysis of predicted gene targets of aberrant miRNAs to find potential pathophysiological pathways.