Erythematous Plaque to Lower Leg After Tropical Injury

A 70-year-old retired nurse presented with a 3-month history of an asymptomatic, nonhealing lesion of her left leg. It developed after she fell and scraped this specific location on her leg on a creek rock while hiking in the jungle during a vacation in Ecuador. She denies any other trauma at any time between the scraping and presentation. After the fall, she subsequently developed an enlarging erythematous plaque with an overlying hemorrhagic crust without drainage. This crust sloughed but soon thereafter reformed. She was treated with triple antibiotic ointment, an antifungal cream, and one week of trimethoprim-sulfamethoxazole prior to presenting to her dermatologist. She was otherwise asymptomatic with a negative review of systems. Past medical history included hypertension, hypercholesterolemia, and hypothyroidism, and her medications were levothyroxine, lovastatin, atenolol, and sodium bicarbonate. She was born in the United States and had not spent any significant time outside the country before this episode. Examination revealed a 2 cm erythematous crusted plaque with several smaller satellite papules on the left shin at the site of trauma (Figure (Figure1A).1A). A punch biopsy (Figure (Figure1B1B and C) and tissue culture were performed. What is the diagnosis? Figure 1. (A) Erythematous eroded plaque with satellite papules on left shin. (B) A 40× magnification demonstrating granulomatous infiltrate. (C) A 100× magnification demonstrating a dermal granuloma with caseous necrosis.