ObjectivesBased on clinical, biomarker and genetic data, autoimmune and autoinflammatory disorders (AIDs) can be classified as a disease continuum from pure autoinflammatory to pure autoimmune with more complex diseases in between. However, the genetic architecture of AIDs has not been systematically described. Here we investigate the polygenic landscape of AIDs using genome-wide association studies (GWAS) and statistical genetics methods to describe this continuum.MethodsWe studied the genetic landscape of 15 AIDs using GWAS summary statistics and methods including genomic structural equation modelling, linkage disequilibrium score regression, Local Analysis of [co]Variant Association, and Gaussian causal mixture modelling (MiXeR). We performed enrichment analyses of tissues and biological gene-sets using MAGMA to highlight shared and distinct perspectives of AIDs.ResultsGenomic structural equation modelling suggested a continuum structure with four underlying latent factors stretching from Crohn’s Disease, Ulcerative Colitis and Primary Sclerosing Cholangitis at one side to Sjogren Syndrome, Systemic Lupus Erythematosus and Systemic Scleroderma on the opposite side. Across AIDs, we observed a balanced mixture of negative and positive local correlations within the major histocompatibility complex, while local correlations outside this region were predominantly positive. MiXeR analysis showed large genetic overlap in accordance with the continuum landscape. MAGMA analysis indicated that genes associated with monogenic immune diseases also play a role in autoimmune (factor 1) and autoinflammatory diseases (factor 4).ConclusionsOur genetic findings support the AIDs continuum. Two of the four clusters, “polygenic autoimmune” and “polygenic autoinflammatory”, reside on margins of this continuum. The identified genetic continuum across different AIDs can potentially guide drug selection, as patients within the same clusters may benefit from the same therapies.