A healthy woman in her 20s presented with a 5-month history of a painful erythematous eruption over her bilateral thighs. She reported that the eruption was worsening during the winter months. She had not experienced any fevers, chills, joint pains, recent weight loss, or any other constitutional symptoms. She was a nonsmoker and took no medications. A review of her social history revealed that she was working at a horse stable and rode for many hours a day. On physical examination, distributed over the bilateral posterior lateral thighs, there were several arcuate to circinate erythematous to violaceous plaques. There were also several focal areas of ulceration with overlying scale-crust (Figure, A and B). A biopsy was performed during this initial visit (Figure, C and D).
Wu J, Baxt R, Jacobson M. Polycyclic Eruption of the Thighs. JAMA Dermatol. 2017;153(1):83-84. doi:10.1001/jamadermatol.2016.3354