Association studies indicate that protein disulfide isomerase is a risk factor in amyotrophic lateral sclerosis

► We performed an association study of the P4HB gene in U.K. ALS cases. ► Genotypes of two SNPs, rs876016 and rs2070872, are associated with ALS. ► Rare haplotypes are overrepresented in ALS cases. ► The functional significance is indicated by effects of genotypes on survival.