A 72-year-old man presented with a 7-day history of an erythematous, mildly pruritic, papular rash over his right upper back area. More papules had developed on the flexor surface of his forearm and on his abdomen a few days after the initial eruption. He denied fever, chills, and difficulty breathing. The pruritus resolved within 24 hours. He did report a biting sensation and, while scratching, discovered a green and yellow caterpillar.
Physical examination revealed several 2- to 4-mm erythematous papules with some excoriations and a few papules with a necrotic center over the right upper back area (Figure 1). A punch biopsy specimen obtained from the rash on the back was sent for histologic examination (Figure 2 and Figure 3).
Christy M. Williams, Kirsten S. W. Bellucci, Vincent Liu, Paul Levins. Erythematous Papular Rash on the Upper Back Area—Quiz Case. Arch Dermatol. 2006;142(11):1501–1506. doi:10.1001/archderm.142.11.1501-b