Hidradenitis suppurativa and inflammatory bowel disease in a nested case-control study

Background: Association between Hidradenitis Suppurativa (HS) and Inflammatory Bowel Disease (IBD) has been suggested. Aims: To assess characteristics of HS and IBD in patients with or without concomitant IBD. Methods: In a prospective, nested case-control study, each IBD patient with concomitant HS (Case) was retrospectively matched with 4 patients with HS and no IBD (Controls) for gender and age (±5 years). HS was classified according to the Hurley score and the International Hidradenitis Suppurativa Severity Score System (IHS4). Data were expressed as mean (Standard Deviation). Statistical analysis included Student-t Test or Mann-Whitney Test, χ2 test, univariate and multivariate logistic regression. Results: The study population included 125 patients with HS: 25 with IBD, 100 matched Controls with no IBD. IBD group included 19 (76%) Crohn’s disease and 6 (24%) Ulcerative Colitis patients. Obesity, familial HS and perianal HS were less frequent in Cases than in Controls (1[4%] vs 25(25%];p = 0.02; 1[4%] vs 21(21%];p = 0.04; 1[4%] vs 31(31%];p = 0.005, respectively).HS was less severe in Cases when assessed by the IHS4 (5.9 ± 4 vs 9 ± 6.7;p = 0.04).Complete drug-induced response for HS was more frequent in IBD (13[53%] vs28 (28%]; p = 0.04). Conclusion: Clinical characteristics of HS and of patients differed between Cases and Controls. Present findings suggest the need to appropriately search and assess skin lesions compatible with HS in IBD.