A 32-year-old woman with a 5-year history of ulcerative colitis presents with a rapidly expanding, exquisitely painful ulcer on her left shin with violaceous undermined edges and a necrotic base. The lesion began as a small pustule 2 weeks ago. Her gastroenterologist suspects pyoderma gangrenosum (PG) and refers her to dermatology. The feature marked **D** in the diagram — pathergy, or worsening with trauma — is a hallmark of PG and has critical implications for management. Which of the following management decisions is MOST appropriate given the presence of pathergy in this patient?

Explanation

## Why Systemic corticosteroids with avoidance of surgery is right Pyoderma gangrenosum is a sterile neutrophilic dermatosis, NOT an infection, despite its name. The pathergy phenomenon (marked **D**) — abnormal worsening of skin lesions in response to minor trauma — is pathognomonic for PG and has a crucial clinical consequence: surgical debridement, drainage, or any traumatic intervention WORSENS the lesion and must be avoided. The correct management is systemic immunosuppression with corticosteroids (IV methylprednisolone pulse for severe disease, followed by oral prednisolone taper) combined with treatment of any underlying systemic disease (in this case, optimization of ulcerative colitis management). This addresses the underlying pathophysiology without triggering further tissue destruction via pathergy. [Robbins 10e Ch 25; Harrison 21e Ch 56] ## Why each distractor is wrong - **Urgent surgical debridement and drainage**: This directly triggers pathergy and will cause rapid expansion and worsening of the ulcer. Surgery is contraindicated in active PG precisely because of the pathergy phenomenon. This is a dangerous management error. - **Empiric broad-spectrum antibiotics and topical antiseptics**: PG is sterile and non-infectious; cultures will be negative. Antibiotics do not address the underlying neutrophilic dermatosis and delay appropriate immunosuppressive therapy. Topical agents alone are insufficient for severe disease. - **Immediate skin grafting after anesthesia**: Skin grafts applied during active PG will fail due to the underlying inflammatory process and pathergy. Grafting is only considered after the disease has become quiescent with immunosuppressive therapy, not during the acute phase. **High-Yield:** Pathergy in pyoderma gangrenosum is the cardinal reason to AVOID surgery and FAVOR systemic corticosteroids or biologics (TNF-α inhibitors) — trauma worsens, immunosuppression heals. [Robbins 10e Ch 25; Harrison 21e Ch 56]