AN UNUSUAL INFECTIOUS CAUSE OF ACUTE URTICARIA

Abstract

Introduction Although many cases of acute urticaria are caused by infectious illnesses, certain pathogens are not frequently reported in association with urticaria. Urticaria Case Description A 28-year-old man presented with 1 week of fevers, neck stiffness and a migratory pruritic rash. His past medical history included asthma and metastatic melanoma that is now in remission. He had received 3 years of pembrolizumab, with the last dose being 1 year prior to presentation. He was non-toxic appearing and had mild nuchal rigidity, a 5 × 7cm well-defined erythematous patch on his back consistent with erythema migrans, and transient, migratory raised plaques on his arms and legs consistent with urticaria. He had a WBC of 12 k with 80.7% neutrophils, and an otherwise normal complete blood count, basic metabolic panel, and liver panel. Lyme IgM was positive, confirmed by Western Blot. CSF revealed 13 nucleated cells with a lymphocytic predominance. He was treated for Lyme meningitis with ceftriaxone 2 g daily. His urticarial rash was controlled with fexofenadine. Upon completion of Lyme treatment, he had no recurrence of urticaria despite discontinuation of fexofenadine. Discussion Infections are a commonly identified cause of acute urticaria with viruses and parasites being the most cited pathogens, and less frequently bacteria. Notably, Lyme disease is not commonly listed as a cause of acute urticaria, although Borrelia burgdorferi has been shown to induce mast cell activation in vitro. This case provides a potential in vivo correlate to these in vitro findings in a patient with concurrent acute urticaria and Lyme borrelliosis. Although many cases of acute urticaria are caused by infectious illnesses, certain pathogens are not frequently reported in association with urticaria. Urticaria A 28-year-old man presented with 1 week of fevers, neck stiffness and a migratory pruritic rash. His past medical history included asthma and metastatic melanoma that is now in remission. He had received 3 years of pembrolizumab, with the last dose being 1 year prior to presentation. He was non-toxic appearing and had mild nuchal rigidity, a 5 × 7cm well-defined erythematous patch on his back consistent with erythema migrans, and transient, migratory raised plaques on his arms and legs consistent with urticaria. He had a WBC of 12 k with 80.7% neutrophils, and an otherwise normal complete blood count, basic metabolic panel, and liver panel. Lyme IgM was positive, confirmed by Western Blot. CSF revealed 13 nucleated cells with a lymphocytic predominance. He was treated for Lyme meningitis with ceftriaxone 2 g daily. His urticarial rash was controlled with fexofenadine. Upon completion of Lyme treatment, he had no recurrence of urticaria despite discontinuation of fexofenadine. Infections are a commonly identified cause of acute urticaria with viruses and parasites being the most cited pathogens, and less frequently bacteria. Notably, Lyme disease is not commonly listed as a cause of acute urticaria, although Borrelia burgdorferi has been shown to induce mast cell activation in vitro. This case provides a potential in vivo correlate to these in vitro findings in a patient with concurrent acute urticaria and Lyme borrelliosis.