Dermoscopy in the differential diagnosis between malar rash of systemic lupus erythematosus and erythematotelangiectatic rosacea: an observational study

Background Malar rash is one of the three cutaneous diagnostic criteria of systemic lupus erythematosus (SLE). Although its clinical recognition is often straightforward, the differential diagnosis with erythematotelangiectatic rosacea may sometimes be challenging. Objective To describe dermoscopic features of SLE malar rash and investigate the accuracy of dermoscopy for the differential diagnosis with erythematotelangiectatic rosacea. Methods A representative dermoscopic image of target areas was evaluated for the presence of specific features. Fisher's test was used to compare their prevalence between the two cohorts, and accuracy parameters (specificity, sensitivity, and positive and negative predictive values) were evaluated. Results Twenty-eight patients were included in the analysis, of which 13 had SLE malar rash and 15 erythematotelangiectatic rosacea. The main dermoscopic features of malar rash were reddish/salmon-coloured follicular dots surrounded by white halos ('inverse strawberry' pattern), being present in 53.9% of the cases, while network-like vessels (vascular polygons) turned out to be the main feature of erythematotelangiectatic rosacea, with a prevalence of 93.3%. The comparative analysis showed that the 'inverse strawberry' pattern was significantly more common in SLE malar rash, with a specificity of 86.7%, while vascular polygons were significantly more frequent in rosacea, with a specificity of 92.3%. Conclusion Dermoscopy may be a useful support to distinguish SLE malar rash and erythematotelangiectatic rosacea by showing peculiar features.