Comparison of Dermatoscopic features between acne vulgaris, acneiform rash and exanthematous pustulosis induced by antitumor therapy: A proposed diagnostic algorithm.

Background Studies devoted to the assessment of dermatoscopic signs in patients with acneiform rashes and acute exanthematous pustulosis induced by antitumor therapy, as well as acne vulgaris are few and do not evaluate differential diagnostic criteria. There are currently no dermatoscopic algorithms available for the differentiation of these conditions. Aim: To assess the dermatoscopic features specific to acneiform rashes in comparison with acne vulgaris and acute exanthematous pustulosis and to develop an algorithm for differential diagnosis. Methods A multicenter, cross-sectional, observational, prospective study was conducted. Adult patients with acneiform rashes associated with antitumor therapy, acne vulgaris, and acute exanthematous pustulosis were included. Dermatoscopic signs were described according to the recommendations of the International Dermoscopy Society for describing of inflammatory dermatoses. Results Acne vulgaris was characterized by brown-yellow clods on skin-colored areas, white-yellow structureless zones with thin branching vessels, pink structureless zones, white clods surrounded by erythema, white structureless zones (p < 0.001), structureless red-brown zones (p = 0.02), and pink follicular fluorescence in UV light. Acneiform rashes demonstrated erythema with telangiectasia (p = 0.02), purpura (p = 0.001), yellow clods surrounded by erythema, a keratin plug in the center of the pustule, purpura, hemorrhagic spots, keratosis follicularis, yellow crusts, pustules surrounded by erythema with telangiectasia, white scales, and under UV dermatoscopy, keratosis follicularis was observed as white follicular fluorescence (p < 0.001). Acute exanthematous pustulosis showed white clods on structureless erythema without specific fluorescence under UV light, although white clods disappeared under UV light. A Venn diagram was used to develop an algorithm for the differential diagnosis of these three disorders. Conclusion Based on a detailed study of dermatoscopic signs and their analysis using Venn diagrams, we developed an algorithm for the differential diagnosis of acneiform rashes, acute exanthematous pustulosis caused by antitumor therapy, and acne vulgaris. The proposed algorithm may be recommended for clinical use.