Trichoscopic Features of Scalp Discoid Lupus Erythematosus versus Lichen Planopilaris: A Systematic Review.

Introduction: Lichen planopilaris (LPP) and discoid lupus erythematosus (DLE) are primary scarring alopecias that pose diagnostic challenges clinically, where trichoscopy features may provide benefit in delineating these two cicatricial alopecia, and also helps in assessing the evolution and therapeutic response. To date, there are few reviews on dermoscopic findings in differentiating these two alopecias. Methods: A systematic literature review was conducted using the PubMed and Google Scholar databases. The search terms included for scalp DLE were 'lupus' OR 'discoid lupus' OR "scalp lupus" and for scalp LPP were "lichen planopilaris" OR "scalp follicular lichen planus" OR "lichen planus follicularis" and were combined with "dermoscopy" OR "dermatoscopy" OR "videodermoscopy" OR "video dermatoscopy" OR "trichoscopy". The differences in the prevalence of dermoscopic features in scalp DLE and LPP were calculated using the Chi-square test. Results: Of 52 articles, 36 (17 LPP, 19 DLE) were eligible for quantitative analysis. We found predominant peripilar tubular casts and perifollicular erythema with the presence of arborizing vessels in the vicinity of these changes, indicating early LPP. In contrast, follicular red dots, speckled brown pigmentation, and hair diameter variability indicated active DLE. Shiny white areas were common in both the groups in late stages. The target pattern of distribution of blue-grey dots, milky red areas, and irregular white fibrotic dots were seen in LPP, and pink-white background, follicular plugs, perifollicular and interfollicular scale, rosettes, chrysalides, and red spider on yellow dots were detected in DLE. Features such as yellow dots and blue-grey structureless areas were nonspecific and did not have a major role in differentiating DLE from LPP. Conclusion: This article provides a comprehensive review of the literature and delineates the trichoscopic differences and peculiarities of scalp DLE and LPP, including the correlation of dermoscopic features with histopathological findings.