A 45-year-old man presents with a localized red plaque on his back (Figure 1). The lesion began 4 years ago as a crusted papule following a puncture wound, caused by the tip of a wooden stick, that resulted in some mild bleeding. The lesion then gradually increased in size and was slightly pruritic on occasion. The patient reports experiencing no fevers or chills since the development of the rash. He was initially diagnosed with eczema in a local clinic and has been treated with intermittent topical application of 2.5% hydrocortisone cream over the last 3 months, with no improvement. On physical examination, a dark red plaque measuring 3.0 × 4.0 cm is observed on the right upper quadrant of the back. The plaque is irregularly shaped with a defined border and includes several black or brown dot-like petechiae. The plaque appears elevated and infiltrative, with a rough surface covered in waxy white crusts. The physical examination is otherwise negative. Cell count, fasting blood glucose level, and results of a tuberculin skin test (purified protein derivative test) are all unremarkable.
Long H, Zhang G, Lu Q. A Persistent Red Crusted Plaque on the Back. JAMA. 2013;310(16):1730-1731. doi:10.1001/jama.2013.280288