A Controversial Relationship Between Crohn's Disease and Hidradenitis Suppurativa: A Case Series and Literature Review.

Crohn's disease (CD) is an inflammatory bowel disease (IBD) with major extraintestinal manifestations. Hidradenitis suppurativa (HS) is a chronic inflammatory skin condition that has previously been described to have a strong association with CD. Though the pathophysiology remains uncertain, this case series highlights the different aspects of disease presentation, similarities, severity, current treatment modalities, and the relational conflict between HS as a paradoxical side effect of biologic agents (BA) that is not well established. We identified a total of three patients with CD and HS and described their clinical presentation and management. A systematic search of the literature with PubMed and Ovid MEDLINE was done in 2021. Two patients were initially diagnosed with CD prior to developing skin manifestations. The third patient was diagnosed with HS first, then was found to have gastrointestinal symptoms. All patients had HS requiring surgical intervention. One patient failed a biological agent but responded to another. The second patient was treated with cytotoxic agents with acceptable results. The third patient was managed without the use of biologics. One of three patients' clinical courses may suggest a paradoxical side effect of BA.  The relationship between CD and HS is based on several case reports. A prospective study will help establish the relationship as well as shed light on the treatment of both conditions simultaneously. In addition, further evaluation of the causal relationship between BA, specifically adalimumab and infliximab as treatment for CD and HS are warranted to effectively manage Crohn's disease, evaluate paradoxical HS, and improve outcomes of both HS and CD. CD and HS impact a patient's quality of life and physicians should therefore have a high degree of awareness upon diagnosis.