All in the family: a population-scale perspective on genetic networks of autoimmune disease.

Autoimmune diseases share a genetic predisposition, and GWAS have identified certain HLA haplotypes as components of susceptibility. In this issue of the JCI, Eriksson et al. leveraged population-scale registry data from Sweden, encompassing 6.3 million individuals in combination with paired relatedness data from a remarkable 3.84 million sibling pairs drawn from 1.57 million nuclear families to create a unified model of the shared genetic risk across 22 common and rare autoimmune diseases. The resulting network of pairwise genetic relationships demonstrated that genetic predisposition alone could not explain the full spectrum of autoimmunity. Analyses exposed distinct patterns, confirmed expected genetic relationships, and revealed unexpected findings. By looking into the family to quantify shared genetic liability at a remarkable scale, this study not only reinforces established genetic components of autoimmune disease but also highlights variation that lacks shared genetic architecture, paving the way for future study of environmental mechanisms in autoimmunity.