C9orf72 and amyotrophic lateral sclerosis: Given the overlap of their clinical and pathological characteristics, the genetic basis of the two disorders has been extensively investigated, and some genes that are highly associated with both diseases have been identified as common genetic causes of ALS and FTD, including chromosome 9 open reading frame 72 (C9orf72), fused in sarcoma (FUS), and TAR DNA binding protein 43 (TDP-43).