A 75-year-old woman with rheumatoid arthritis, treated with long-term prednisone, and genital herpes simplex virus 2 presented with a 1-week history of a painful, pruritic rash on the left buttock. She denied any recent trauma to the area or any new skin exposures. She denied experiencing fevers, lymphadenopathy, and other constitutional symptoms. Of note, she had recently tapered her prednisone dose from 10 mg to 5 mg, with subsequent flare of her rheumatoid arthritis, after which she started pregabalin for pain 3 days before her eruption. Following rash onset, she had also started valacyclovir for 1 week, without benefit. She was not receiving other treatments for rheumatoid arthritis, such as nonsteroidal anti-inflammatory drugs or anti–tumor necrosis factor alpha (anti–TNF-α) therapies. Physical examination revealed warm, indurated, and well-circumscribed erythematous plaques, with subtle vesicles and collarettes of scale, on the left buttock (Figure). Edema, erythema, and pain of the left wrist joint were also noted. The remainder of the physical examination was unremarkable.
Tan CZ, Novoa R, Chen JK. Erythematous Plaques on the Buttock. JAMA. 2016;315(1):79-80. doi:10.1001/jama.2015.13562