The Margin That Moved by the Hour

A 52-year-old man with no significant medical history scrapes his left shin on a rose trellis while gardening. He rinses the abrasion at home and thinks little of it. He takes no medications, drinks alcohol in moderation, and has no history of diabetes, immunosuppression, or chronic liver or kidney disease.

Roughly thirty hours later he presents to the emergency department with severe, unremitting leg pain that seems far worse than the wound appears, along with fevers and shaking chills. Over the next six hours the erythema advances across his shin at a rate the nurses document in centimeters per hour, crossing the knee and creeping up the thigh despite elevation, and he becomes increasingly confused.

On examination his temperature is 39.4 °C, heart rate 132/min, blood pressure 82/50 mmHg, and respiratory rate 26/min. The left leg is tense, hot, and wood-hard to palpation, with a dusky violaceous patch and a flaccid hemorrhagic bulla; tenderness extends well beyond the visible margin, yet light touch over the central area is paradoxically blunted, suggesting cutaneous nerve destruction. Laboratory studies show a white blood cell count of 27.5 × 10³/µL with 19% bands, sodium 131 mmol/L, creatinine 2.3 mg/dL (baseline 0.9), INR 1.7, platelets 88 × 10³/µL, lactate 4.8 mmol/L, and creatine kinase 2,400 U/L.

Blood cultures and fluid aspirated from a fresh bulla are obtained. Within twelve hours the blood culture bottles flag positive, and the Gram stain is shown below.