Urticaria Multiforme in an Elderly Patient: A Case Report.

Urticaria multiforme is a morphological variant of urticaria, clinically characterized by arciform urticarial plaques, more commonly observed in children, with a benign and self-limited course. We present the case of a 72-year-old female who acutely developed fever and a disseminated dermatosis characterized by arciform and annular urticarial plaques, erythemato-violaceous with a pale center, accompanied by angioedema of the upper lip. Given the clinical findings and in order to exclude differential diagnoses with greater systemic involvement, a skin biopsy was performed, revealing superficial dermal edema and a superficial perivascular mixed inflammatory infiltrate with few eosinophils. Based on the histopathologic evidence, which excluded major differential diagnoses such as vasculitis and erythema multiforme, as well as the absence of systemic involvement, a diagnosis of urticaria multiforme was established. Due to the extent of the lesions, systemic corticosteroid therapy was initiated, resulting in complete remission without recurrence. Finally, antibiotic use and a recent upper respiratory viral infection were identified as associated factors. This case highlights the importance of considering this diagnosis in adults, allowing for prompt recognition and avoiding overtreatment given its benign course.