The lesions are from the arm of a 35-year-old man (Figure 1) (scale indicates millimeters), the trunk of a 15-year-old girl (Figure 2), the leg of a 51-year-old woman (Figure 3), and the leg of a 20-year-old woman (Figure 4). All patients had erythematous, urticariform lesions. The first 2 patients had common urticaria, and the others had urticarial vasculitis. The handheld dermoscope (×10 original magnification) serves to clinically discriminate between these diseases noninvasively. Figure 1 and Figure 2 show common urticaria dermoscopically, disclosing prominent, sometimes reticular red lines. These red lines correspond histologically with ectatic, horizontal, subpapillary vessels and are different from vascular red dots (papillary vessels). Lesions of common urticaria may also show structureless avascular areas, devoid of vascular findings, representing areas where the vessels are obscured by prominent edema (Figure 2). Purpuric structures are not seen in common urticaria wheals. Figure 3 and Figure 4 show urticarial vasculitis dermoscopically disclosing purpuric dots or globules in a patchy orange-brown background. These structures are associated with extravasation and degradation of red blood cells. Red lines and purpuric globules are not specific to urticaria and urticarial vasculitis, respectively; however, the recognition of these structures will help as a first-line clinical screening tool for discriminating between common urticaria and urticarial vasculitis in daily practice.
Vázquez-López F, Fueyo A, Sánchez-Martín J, Pérez-Oliva N. Dermoscopy for the Screening of Common Urticaria and Urticaria Vasculitis. Arch Dermatol. 2008;144(4):568. doi:10.1001/archderm.144.4.568