Objective: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease associated with inflammatory bowel disease (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC). This study aimed to assess the prevalence and clinical characteristics of HS in a population-based cohort of newly diagnosed IBD patients.

Methods: The Copenhagen IBD Inception Cohort is a population-based inception cohort of newly diagnosed patients with IBD between May 2021 and April 2023. IBD-related clinical data and extraintestinal manifestations (EIMs) were collected, with HS identified through validated self-reported questionnaires and dermatological examinations. Statistical comparisons were performed between IBD patients with and without HS.

Results: Of 527 patients with new-onset IBD, 38.1%, 58.4%, and 3.4% had CD, UC, or unclassified IBD, respectively. HS was prevalent in 5.5% (n=29), 8% (n=16), and 3.9% (n=12) of patients with CD and UC, respectively. Patients with concomitant HS were most frequently affected in the groin area and buttocks, had significantly higher BMI (26.4 vs. 24.2 kg/m², p=0.036), and had higher prevalence of EIMs (79.3% vs. 41.2%, p<0.001) compared to patients with IBD alone. Among CD patients, those with HS had higher disease activity (Harvey-Bradshaw Index: 9.6 vs. 6.8, p=0.029) and more frequent perianal disease (31.3% vs. 9.7%, p=0.023).

Conclusions: HS is a prevalent comorbidity in newly diagnosed IBD patients. Concomitant HS is associated with increased BMI, a higher burden of EIMs, and greater disease severity. Early dermatological assessment and integrated management strategies are essential to optimize care for these patients.