A 5-year-old boy presented with three months of deeply erythematous papules in a serpiginous arrangement on his lateral abdomen. The lesions were painless and non-pruritic.

His parents could recall nothing being applied to the skin in that area prior to the eruption, and no treatments had been attempted. He was otherwise healthy and had no other close contacts with similar skin findings.

What is the most likely diagnosis?

(Please select 1 option)