Burning Finger

A 32-year-old nurse came to the clinic with severe pain and swelling in her left thumb. She reports that these symptoms began two days ago and have been progressively worsening. The pain, rated 6 out of 10, is associated with a burning sensation. She is concerned about the pain and discomfort, which are affecting her ability to work. She has no significant past medical history and is otherwise healthy. She also denies a history of trauma or injury to the thumb. Her vitals are normal except for a temperature of 37.8 °C. Her physical examination reveals grouped vesicles on an erythematous edematous base, filled with fluid, associated with swelling, erythema, and tenderness of the left thumb, as shown in the image. There are no signs of vesicles elsewhere on the body. She is in a long-term, monogamous relationship with her partner. Which of the following diagnoses is most likely