Large Study Uncovers Distinct Genetic Links Across Autoimmune Diseases
Autoimmune diseases often cluster within families, and people with one autoimmune disease may be more likely to develop another. This pattern suggests that some autoimmune conditions may share underlying genetic risk factors. A large nationwide study from Sweden has now mapped how strongly 22 autoimmune diseases appear to be genetically connected and found that those connections tend to cluster by the tissues and organ systems they affect.
More than 6.3 million people and 3.8 million sibling pairs
Researchers analyzed national health and family registry data from 6,336,615 people born in Sweden between 1932 and 1983, including nearly 3.84 million full-sibling pairs. Diagnoses of 22 autoimmune diseases were tracked from 1969 through 2013. By comparing how often the same or different autoimmune diseases appeared among siblings, the researchers estimated the degree of shared genetic risk between conditions.
Across the full study population, 707,995 people, or 11.2%, had at least one of the autoimmune diseases studied. Autoimmune disease was more common among women than men, affecting 15.3% of women compared with 7.2% of men.
Autoimmune diseases were genetically connected, but not all in the same way
The researchers found a broad network of genetic relationships across autoimmune diseases, but some conditions shared much more genetic risk than others.
Some of the strongest genetic links were seen between:
- Psoriasis and psoriatic arthritis: genetic correlation = 0.84*
- Autoimmune hepatitis and primary biliary cholangitis: genetic correlation = 0.68
- Systemic lupus erythematosus and Sjögren disease: genetic correlation = 0.61
* A genetic correlation closer to 1 indicates that two conditions share more of the same genetic influences, while a value closer to 0 indicates little shared genetic influence. The 0.84 correlation between psoriasis and psoriatic arthritis therefore represents a particularly strong genetic overlap.
At the other end of the spectrum, some autoimmune diseases appeared to have very little shared genetic risk. Type 1 diabetes and psoriasis had a genetic correlation close to zero, and multiple sclerosis generally showed weak genetic connections with the other autoimmune diseases studied.
Genetic similarities tended to follow affected tissue type
When the researchers grouped diseases according to the strength of their genetic relationships, clearer clusters emerged among connective tissue diseases, endocrine autoimmune diseases, gastrointestinal disorders, and liver-related autoimmune diseases. Diseases affecting the nervous system showed much less internal clustering.
Importantly, the study found no evidence of a single strong genetic factor that broadly predisposes people to all autoimmune diseases. Instead, the findings suggest that shared genetic risk is concentrated within particular groups of related conditions.
Citation
Eriksson, D., Kuja-Halkola, R., Holmqvist, M. E., Larsson, H., Butwicka, A., Gudbjörnsdottir, S., Kämpe, O., Bensing, S., & Skov, J. (2026). Tissue-specific clustering of genetic correlations across autoimmune diseases in a nationwide sibling study. The Journal of clinical investigation, e205952. Advance online publication. https://doi.org/10.1172/JCI205952