“It is often observed that bowel diseases and psoriasis occur together. We took this as an opportunity to investigate whether there is a causal association between these two diseases," explains Dr. Dennis Freuer, research associate at the Chair of Epidemiology and first author of the study. “To do this, we used what is called the Mendelian randomisation approach. In the context of this method, we used mathematical models to process the genetic information of almost half a million people that were available from genetic studies,” the statistician continues. If the genetic information is related to both diseases in a very characteristic way, mathematically sound conclusions can be drawn about causal relationships.

Inflammatory bowel disease increases the risk of psoriasis

The results were clear. If a person suffers from a chronic inflammatory bowel disease, the risk of psoriasis developing later, with or without joint inflammation, increases. Conversely, however, no association could be demonstrated. Subgroup analyses suggested that Crohn's disease in particular, and not ulcerative colitis, is responsible for the increased risk. Further studies are now needed to clarify the exact nature of the disease processes in the body. However, the results of the current study are already of great importance for medical care, as they not only contribute to a better understanding of how psoriasis develops, but also make it clear that the disciplines responsible for the two diseases will have to work together in future when it comes to diagnosis and treatment. "It is important that general practitioners and gastroenterologists, who are primarily responsible for the care of patients with chronic bowel diseases, know that these patients are at increased risk of psoriasis. They should pay particular attention to skin symptoms or joint problems occurring in patients with inflammatory bowel disease, to initiate early an appropriate treatment," adds Prof. Christa Meisinger, senior author of the study.

Publication:
Freuer D, Linseisen J, Meisinger C. Association Between Inflammatory Bowel Disease and Both Psoriasis and Psoriatic Arthritis: A Bidirectional 2-Sample Mendelian Randomization Study. JAMA Dermatol. Published online September 14, 2022. doi:10.1001/jamadermatol.2022.3682