Background: Psoriasis, psoriatic arthritis (PsA), and inflammatory bowel disease (IBD) are related inflammatory immune-mediated diseases, with considerable overlap. However, it is as yet unclear whether co-occurrence of these diseases affects disease course and characteristics of the individual complaints. The objective of this study was to identify the prevalence of IBD and PsA in a psoriasis cohort and to examine whether patients with concurrent psoriasis and IBD carry a distinct phenotype. Methods: Data of all patients with psoriasis visiting a general hospital in the Netherlands between 2009 and 2014 were retrospectively retrieved from electronic patient files. In addition, clinical characteristics of patients with concurrent psoriasis and IBD (n = 40) were compared with psoriasis-only (n = 1643) and IBD-only (n = 385) cohorts. Results: Among 1669 hospital-based patients with psoriasis, prevalence of PsA was 12.2% (n = 203, 95% confidence interval, 10.5-13.7) and of IBD 1.6% (n = 26, 95% confidence interval, 1.0-2.2), including 12 Crohn's disease (CD) and 14 ulcerative colitis. Psoriasis-PsA patients were more likely to have IBD than psoriasis-only patients (3.0 versus 1.4%). Psoriasis-CD patients were younger at CD diagnosis (20.0 versus 32.0 yr, P = 0.001), and psoriasis diagnosis (28.0 versus 43.5 yr, P = 0.004) than psoriasis-only patients. Psoriasis-IBD patients had a mild psoriasis phenotype similar to psoriasis-only patients, but the CD-phenotype was significantly more severe than in CD-only patients. Conclusions: The prevalence of IBD in psoriasis was approximately 4 times higher than that in the general population, with the highest risk for psoriasis-PsA patients. Psoriasis-CD patients have a mild (early-onset) psoriasis but an earlier-onset and severe CD-phenotype.

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Keywords comorbidity, epidemiology, IBD, phenotype, psoriasis
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Journal Inflammatory Bowel Diseases
Eppinga, H, Poortinga, S. (Sietske), Thio, H.B, Nijsten, T.E.C, Nuij, V.J.A.A, van der Woude, C.J, … Peppelenbosch, M.P. (2017). Prevalence and Phenotype of Concurrent Psoriasis and Inflammatory Bowel Disease. Inflammatory Bowel Diseases, 23(10), 1783–1789. doi:10.1097/MIB.0000000000001169