Concomitant Crohn's Disease and Hidradenitis Suppurativa With Severe Stricturing Peri-Anal Disease

Introduction: Crohn’s disease (CD) is an inflammatory bowel disease that presents with both intestinal and extraintestinal manifestations. While a clinically different presentation, hidradenitis suppurativa (HS) shares CD’s inflammatory presentation, forming debilitating sterile skin abscesses, scarring, sinus tracts, perianal fistulas, and stenosis. This case describes a case of active Crohn's flare, but with extensive history of HS, obfuscating the clear etiology of the patient’s anocutaneous fistulas and acute on chronic anal stenosis. Case Description/Methods: A 43-year-old man, with a history of tobacco use, recently diagnosed CD and longstanding pelvic HS, presents with perirectal drainage and anal stenosis (Image A/B). Initial CT imaging showed anocutaneous fistulas extending into the bilateral gluteal skin surfaces, circumferential mural thickening from anus to descending colon, and perineal, gluteal, and thigh HS (Image C). The patient reported poor compliance with his mesalamine therapy but reported relatively good control of his pelvic HS up until this point, which had previously undergone debridement, skin grafting/flaps, and diverting colostomy with anoplasty. Colonoscopy revealed significant anal stenosis within the gluteal folds from previous HS interventions, a stenotic bowel lumen 25 cm from the anus that was un-advanceable, and circumferential inflammation and deep ulcerations within the rectum (Image D). Biopsy revealed severe active chronic colitis consistent with Crohn’s flare. The patient was subsequently started on a prednisone taper with the intention to follow up for anti-TNF alpha therapy (Figure 1). Discussion: While no clear correlation between CD and HS has been clearly established, recent studies have suggested an association between the 2 disease processes. Both diseases have been associated with elevated inflammatory factors, such as IL-1, IL-6, IL-17, IL-23, and TNF, hence the use of biologics in the treatment of severe stages of both diseases. Patients with IBD also have a 9 times increased risk of developing HS compared to the general population. Despite prior well managed HS, a flare of the patient’s CD led to formation of anocutaneous fistulas and exacerbation of existing anal stenosis. This case highlights the interconnected prevalence and possible synergistic effect of the 2 diseases in the setting of perianal disease. The presence of gastrointestinal symptoms and concomitant HS perianal disease should prompt colonoscopy evaluation for a potential Crohn’s flare.Figure 1.: A) Severe hidradenitis suppurative involving perineum, bilateral gluteal and upper superior right thigh soft tissues and bilateral complex anocutaneous fistulas of the right and left gluteal skin surfaces. B) Gross anal stenosis present on colonoscopic evaluation. C) CT abdomen and pelvis with evidence of severe HS and anocutaneous fistulas. D) Colonoscopic evaluation with circumferential deep ulceration at the rectum with stenotic bowel 25 cm from the anus.