Van Vugt et al. report that genotyping 39 disease-associated short tandem repeats (STRs) in 8531 Project MinE samples revealed pathogenic C9orf72 and ATXN2 expansions significantly associated with amyotrophic lateral sclerosis, with C9orf72 linked to earlier onset and reduced survival. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.