Table 1.

Differential diagnoses and features of urticarial vasculitis.

Differential diagnosis	Features
Chronic idiopathic urticaria	Individual lesions lasting <24 hours
Well’s syndrome	Usually a small number of lesions with intensively eosinophilic infiltrate on histology
Erythema migrans	Annular erythema and other features of Lyme borreliosis
Tumid lupus erythematosus	Annular plaques on sun-exposed areas that are fixed and have a characteristic histology
Urticarial phase of bullous pemphigoid	Evolves to characteristic blistering lesions with diagnostic routine microscopic and immunomicroscopic changes
Schnitzler syndrome	Chronic urticarial rash showing neutrophilic dermal infiltrate on histology; no evidence of vasculitis present
Urticarial multiforme	Classic target lesion with violaceous or dusky center that may blister