Clinical Characteristics of Patients Presenting with Moderate-to-Severe Atopic Dermatitis and Concomitant Inflammatory Bowel Diseases: a Multicenter Retrospective Study

Introduction: Atopic dermatitis (AD) and inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic immune-mediated disorders with overlapping immunopathogenic mechanisms. Limited research has investigated clinical features of AD and concomitant IBD. Objectives: This study aimed to evaluate the clinical presentation of adult patients with concomitant moderate-to-severe AD and IBD. Methods: Adult patients with moderate-to-severe AD and confirmed IBD were identified across 12 hospital-based dermatology centers between 2022 and 2024 by using electronic records. Results: Thirty-eight out of 4,236 (0.9%) patients with moderate-to-severe AD had verified IBD (19 CD and 19 UC), with a prevalence higher than that expected in the general Italian population (0.9% vs 0.41%). The mean age at AD diagnosis was 25 years, with AD preceding IBD diagnosis with a median interval of 10 years in 71% of cases. At the time of the study, 40% of CD patients and 63% of UC patients were in clinical remission. AD clinical presentation in patients with IBD was typical, with 68% of patients presenting with flexural phenotype, and associated with personal (34%) or family (40%) history of atopy. Conclusions: IBD is not frequent in AD patients, but the prevalence seems to be higher compared to the general population. AD occurring with IBD had a typical clinical presentation. Interestingly, occurrence of AD preceded IBD onset in most patients, putting dermatologists in the position to make early IBD diagnosis. However, no direct causal relationship can be drawn from these findings. Larger, controlled prospective studies are needed to clarify the relationship between AD and IBD.