S4911 Mistaken for Infection: Delayed Recognition of Pyoderma Gangrenosum in a Crohn’s Flare

Introduction: Pyoderma gangrenosum (PG) is a rare but severe neutrophilic dermatosis associated with inflammatory bowel disease (IBD). We present a case of PG triggered by a severe Crohn’s flare highlighting diagnostic challenges and management strategies. Case Description/Methods: A 19-year-old man with a history of Crohn’s disease, previously diagnosed as ulcerative colitis, presented with worsening bloody diarrhea and a painful, enlarging right thigh lesion and multiple smaller lesions in his bilateral lower extremities. His medical history was notable for perianal abscesses and fistulas. Home medications included azathioprine (1600 mg/day), mesalamine, and low-dose prednisone (5 mg daily). On admission, he was febrile with leukocytosis (WBC 16.3 K/µL), C-reactive protein 24.8 mg/dL, erythrocyte sedimentation rate 77 mm/hr, and stool calprotectin >5040 µg/g. Computed tomography imaging revealed a left thigh fluid collection initially interpreted as an abscess. Colonoscopy demonstrated severe colitis with deep ulcerations, pseudopolyps, and a suspected colonic fistula. A transthoracic echocardiogram showed no vegetations, and bacteremia was ruled out. Azathioprine was discontinued, and intravenous methylprednisolone (40 mg daily) was started for a severe Crohn’s flare. General surgery was consulted early and performed multiple drainages of the thigh lesion, but the wound continued to enlarge and remained painful despite broad-spectrum antibiotics (cefepime and daptomycin). The lack of clinical improvement raised concern for PG and prompted Dermatology consult. A punch biopsy confirmed PG. Dermatology recommended avoiding surgical debridment due to concern for pathergy. The patient’s condition improved on intravenous steroids. He was discharged on a prednisone taper and later initiated on vedolizumab for maintenance IBD therapy. At 3-month follow-up, his skin lesions had nearly completely resolved. Discussion: PG is a rare extraintestinal manifestation of IBD, affecting 1%–2% of Crohn’s patients. It is an autoinflammatory disorder driven by neutrophilic dysfunction, often misdiagnosed as infection due to painful ulcerations. Biopsy is essential to confirm PG and exclude mimics. Surgical debridement is contraindicated due to pathergy. Treatment includes corticosteroids, immunosuppressants, or biologics. In this case, steroids and vedolizumab led to near-complete resolution, highlighting the need for early diagnosis.