The Gardener's Finger

A 46-year-old woman presents with 5 weeks of a slowly progressive lesion on the right index finger and several new nodules extending up the same arm. The lesion began as a small papule and has become more erythematous and ulcerated. She now notes mild tenderness but no drainage, fever, or systemic symptoms.

She is otherwise healthy and takes no medications. Six weeks earlier, she spent a weekend pruning rose bushes and repotting plants and remembers a thorn puncture to the affected finger. She denies cat scratches, aquarium exposure, recent travel, or immunocompromising conditions.

Temperature is 36.9 C, heart rate 78/min, blood pressure 122/74 mmHg, and oxygen saturation 99% on room air. Examination shows an indurated erythematous papulonodule with central crusting over the dorsal right index finger and 2 smaller subcutaneous nodules tracking proximally along the forearm. There is no fluctuance, purulence, or flexor tendon sheath tenderness.

White blood cell count is 6.8 x 10^3/uL, creatinine is 0.8 mg/dL, and C-reactive protein is mildly elevated. She completed 7 days of cephalexin without improvement. A superficial bacterial swab culture is unrevealing, and plain radiographs show no foreign body or osseous abnormality.