To determine the prevalence of psoriasis in an IBD cohort with reference to clinical characteristics and anti-TNFα use.
Patients with psoriasis and IBD were retrospectively identified from the IBD database at Tallaght Hospital from 2000 to 2015. Pertinent clinical data were obtained from patients notes including anti-TNFα exposure. Prevalence rates of genuine and reactive psoriasis were calculated and compared using Student's T -test. A P values of <0.05 was considered significant.
In total, 1384 IBD patients were identified. The overall prevalence rate of IBD and psoriasis was 2.4% ( n  = 33), with 1.8% ( n  = 25) in the Crohn's disease group and 0.6% ( n  = 8) in the ulcerative colitis group. Within the psoriasis group, 24% ( n  = 8 of 33) had reactive psoriasis. The prevalence rates of psoriasis in the non-biological and biological cohorts were similar 2.5% (25 of 981) and 2% (8 of 403), respectively. There was no significant association with reactive psoriasis and disease type. There was a trend towards higher rates of reactive psoriasis Adalimumab users, 3.6% (6 of 166) vs. 0.8% (2 of 237), OR = 4.283, P  = 0.077, 95% CI 0.854-21.483 in infliximab users. In addition, in our cohort, smoking was not associated with any form of psoriasis in IBD, OR = 1.377, 95% CI 0.061-3.087, P  = 0.437.
In our large study, the prevalence rate of reactive psoriasis was similar to the background rate of psoriasis in the overall IBD cohort (2.0 vs. 2.4%). A 2% prevalence rate represents a common adverse event that clinicians should be aware of.