Differential diagnosis of linear eruptions in children

A 3-year-old girl presented with a linear eruption on her leg for 2 months. She was otherwise healthy and well-appearing. Physical examination showed many small, erythematous, flat-topped papules coalescing into a linear erythematous plaque. At a follow-up visit 9 months later, the eruption had resolved, leaving postinflammatory hypopigmentation.When approaching a cutaneous eruption, appreciating the pattern of the lesions can be instrumental to arriving at the correct diagnosis. For this patient with the acute onset of a plaque on the leg, the differential diagnosis is narrowed by the linear distribution of the skin lesions. The differential diagnosis of linear eruptions in children includes lichen striatus, linear lichen planus, linear psoriasis, inflammatory linear verrucous epidermal nevus, incontinentia pigmenti, phytophotodermatitis, and allergic contact dermatitis. Of note, many of these conditions manifest in a linear manner as a result of cutaneous mosaicism, whereas others are caused by external agents contacting the skin.