A 3-year-old child presents with widespread vesicles on the lips, tongue, and oral mucosa. After 2 to 4 days, these vesicles break down, leading to the formation of a pseudomembrane. Additionally, some skin lesions are observed. What is the most likely diagnosis?

Explanation

The clinical presentation of widespread oral vesicles that rupture and form pseudomembranes along with skin lesions is characteristic of erythema multiforme (EM). Herpetic stomatitis typically involves painful vesicles but does not usually cause pseudomembrane formation or widespread skin involvement. Acute necrotizing ulcerative gingivitis primarily affects the gums without widespread vesicles, and Stevens-Johnson syndrome presents with more severe mucocutaneous involvement. Thus, the correct diagnosis is erythema multiforme.