Shared genetic loci between Alzheimer's disease and multiple sclerosis: Crossroads between neurodegeneration and immune system

•Alzheimer's disease and multiple sclerosis have similar polygenicities and a similar estimated number of associated variants with the trait (1.8 thousand).•Alzheimer's disease and multiple sclerosis show prominent genetic overlap (20%) despite weak genetic correlation, implying mixture of concordant and discordant effects across shared genetic variants.•We identified 16 shared genetic loci between Alzheimer's disease and multiple sclerosis with mixed effect directions.•Functional analyses of the shared loci implicated immune pathways in the pathogenesis of Alzheimer's disease.