Frequency of pathergy phenomenon and other features of Behçet's syndrome among patients with inflammatory bowel disease.

Objective: Crohn's disease (CD) and ulcerative colitis (UC) share common clinical features with Behçet's syndrome (BS). We surveyed UC and CD patients for pathergy phenomenon and features of BS with the aim of determining how much overlap is present between these 2 entities in a setting where BS is relatively common, the frequency of pathergy positivity in inflammatory bowel disease (IBD) patients and evaluating how International Study Group (ISG) criteria perform in differentiating IBD from BS.
Methods: This study was conducted among patients with CD and UC attending the gastroenterology outpatient clinic of a university hospital which is also a referral center for BS. Consecutive CD and UC patients were screened for BS using ISG criteria. Pathergy test was performed and evaluated by 2 independent observers in a masked manner.
Results: Ninety-three patients with CD and 130 with UC were surveyed. None of the CD patients fulfilled ISG criteria for BS while 2 of 130 UC patients did. Twenty CD patients had oral ulcers while 4 reported having genital ulcers but no scars could be observed. Twenty-two CD patients had papulopustular lesions, 2 had nodular lesions, 3 had arthritis and none had uveitis. Thirty-two UC patients had oral ulcers, none had genital ulcers, 23 had papulopustular lesions, 3 had nodular lesions, 2 had arthritis and 2 had uveitis. Pathergy test was positive according to at least one of the observers in 10/93 CD and 8/130 UC patients and according to both observers in 4/130 UC patients.
Conclusion: Despite similarities between the clinical features of CD and UC with BS, coexistence is uncommon. ISG criteria perform well in differentiating these diseases. About 8% of IBD patients show the pathergy phenomenon.