Impetigo

A 5-year-old boy presents to the pediatric clinic with a 4-day history of spreading lesions around the mouth and nostrils that began as small red spots after a minor scrape. The lesions rapidly evolved into vesicles that ruptured and formed crusts. On examination, the child is afebrile and interactive. Cutaneous examination reveals multiple erythematous macules that have evolved into vesicles and pustules, with several lesions displaying the characteristic thick golden-yellow crusts overlying an eroded base, as marked by **A** in the diagram. The lesions are located primarily on the perioral skin, nasolabial folds, and chin. Based on the morphology marked **A**, what is the most likely diagnosis?