As well as ALS, C9orf72 GGGGCC repeat expansions are commonly found in FTD, and the spectrum of C9orf72 diseases extends from both ALS and FTD to other motor disorders such as primary lateral sclerosis (PLS), progressive muscular atrophy (PMA), and Huntington’s disease (HD) phenocopies, as well as other non-motor disorders, such as Alzheimer’s disease (AD). The gene discussed is C9orf72; the disease is Alzheimer disease.