Normocomplementemic urticarial vasculitis secondary to Lyme disease: A rare association with challenging treatment.

Urticarial vasculitis (UV) is a rare entity characterised by long-lasting recurrent episodes of urticarial lesions. Although frequently idiopathic, UV has been associated with multiple diseases, including infections. We present a case of Lyme disease (LD) as a trigger of normocomplementemic UV, a very rarely described association. The patient presented first with episodes of inflammatory polyarthritis and a positive serology for Borrelia burgdorferi , later followed by the appearance of long-lasting urticarial lesions, histologically suggestive of UV. Lyme arthritis resolved with doxycycline, but UV persisted. Response to cyclosporine was satisfactory but with side effects, and only methotrexate showed substantial and consistent improvement. This case reminds physicians that chronic urticaria with atypical characteristics should raise suspicion of UV. Possible triggers for this disease must be sought, even if rarely described, such as LD. Normocomplementemic UV frequently presents a therapeutic challenge, but methotrexate can be a particularly effective therapy in this setting.