Identification of Clinical and Genetic Parameters Associated with Hidradenitis Suppurativa in Inflammatory Bowel Disease

Background: Hidradenitis suppurativa (HS) has recently been associated with inflammatory bowel disease (IBD). The objective of this study is to investigate the prevalence of HS in IBD and to identify clinical and genetic parameters associated with HS in IBD. Methods: A questionnaire, validated for HS, was sent to 1969 patients suffering from IBD. Results: The prevalence of HS in our IBD cohort (1260 participating patients) was significantly higher than in the general population (6.8%-10.6% versus 1%-2%). IBD patients with HS were affected by IBD significantly earlier and more often treated with anti-TNF-alpha therapy and surgical resection compared to IBD without HS. Female gender, smoking, a higher body mass index, and younger age were independent associated parameters for HS. Within cases allelic association analysis was performed for 59 cases (IBD with HS) and 293 controls (IBD without HS). We observed 2 promising new associations in genomic regions harboring ELOVL7 (rsnumber 10057395 P = 7.15 x 10(-5), odds ratio = 0.4), and in the intergenic region between SULT1B1 and SULT1E1 (rsnumber 2014777 P = 7.48 x 10(-5), odds ratio = 2.3). Conclusions: HS is present in 6.8% to 10.6% of IBD patients. Co-morbid HS is associated with an early onset of IBD in which anti-tumor necrosis factor-a therapy and surgical resections are often needed. We identified a suggestive protective association with ELOVL7 and suggestive risk association with the genes SULT1B1 and SULT1E1 for HS, in the context of IBD. These genetic associations need further exploration and replication in additional independent cohorts.