Introduction:

The rash in pediatric patients is often a challenge in daily clinical practice, as it can be associated with a wide variety of disorders, some with isolated cutaneous symptoms, others with systemic involvement, from benign and self-limited illnesses to more serious conditions that may require specific treatment. The authors report a case of urticaria multiforme with the aim of analyzing the semiological aspects of this pathology, its benign character, the differential diagnoses to be considered and the therapy to be instituted.

Case report:

Eleven-month-old male infant, without major pathological history, was brought to the emergency department for an evanescent rash and peripheral edema with approximately 24 hours of evolution, without fever nor other associated complaints. He had finished amoxicillin with clavulanic acid due to acute otitis two days before being brought to the emergency department. On physical examination, a maculopapular rash stood out, with annular, polycyclic lesions, with an erythematous halo and a clear center, located on the face, trunk, and limbs, pruritic, associated with slight edema of the hands, feet, and face, without petechiae nor affecting the mucous membranes. No other relevant findings. Laboratory tests were not necessary, and the patient was discharged with a diagnosis of urticaria multiforme, with post-infectious/post-pharmacological association, treated with oral antihistamine and corticosteroids. Complete resolution of the lesions occurred approximately 48 hours later.

Comment:

Urticaria multiforme is a benign and self-limited disorder that appears mainly in pediatric age, characterized by the appearance of an erythematous maculopapular rash, with annular, polycyclic lesions, evanescent, easily mistaken with other more severe illnesses. Initially, it may be similar to erythema multiforme, serum sickness-like reaction, urticarial vasculitis, and acute hemorrhagic edema of infancy, however, these entities represent different pathologies, with different approaches and prognoses, therefore the clinical distinction between them is extremely important.

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