S1703 Erythema Nodosum as a Marker for Objective Disease Activity in Inflammatory Bowel Disease

Introduction: Erythema Nodosum (EN) is an inflammatory condition characterized by tender, erythematous nodules, typically found on the extensor surfaces of the extremities. In patients with IBD, EN is the most common cutaneous manifestation, affecting 3–10% of those with ulcerative colitis (UC) and 4–15% with Crohn’s disease (CD), particularly in patients with colonic involvement. While EN has been thought to correlate with disease activity, no definitive correlation with objective measures, such as Inflammatory markers or endoscopic activity have been established. Methods: The IBD Centre of British Columbia is a tertiary, multidisciplinary clinic with a patient registry containing over 6,500 IBD patients. Patients with active EN were identified and symptomatic disease activity was assessed. Objective assessments included colonoscopy, cross-sectional imaging (CT/MRI), fecal calprotectin and CRP. Descriptive statistics were used to evaluate between objective and subjective measures of disease activity and the presence of EN. Results: Of 169 patients with documented EN, 95 had at least one objective assessment within the prespecified timeframe and were included. The mean age at presentation of EN was 32 years. The majority had CD (80%), and were women (75%). Among CD patients, 93% had colonic involvement and 32% had penetrating disease. A total of 77 (74%) patients had gastrointestinal symptoms at the time of EN presentation and 84 (81%) had objective evidence of active disease. Colonoscopy was performed in 66% of cases, with 58 patients (84%) showing active inflammation. Among CD patients, 53% had mucosal ulcerations, while 67% of UC patients had severe disease (Mayo E3). Conclusion: In this cohort, most patients presenting with EN had both symptomatic and objective signs of intestinal inflammation. These findings support the use of objective testing in IBD patients with EN and suggest EN may indicate a more severe or complicated disease course.