Dermoscopic characterization of guttate psoriasis, pityriasis rosea, and pityriasis lichenoides chronica in dark skin phototypes: An observational study.

Dermoscopy as a diagnostic tool is attaining impetus in inflammatory dermatoses with the cumulative description of characteristic findings in most dermatoses obviating at times the need of biopsy. In this retrospective observational study, 20 histopathology confirmed cases each of pityriasis rosea (PR), guttate psoriasis (GP), and pityriasis lichenoides chronica (PLC) seen over a period of 3 years were included. Dermoscopy images were extracted from photography archives for evaluation and three lesions from each patient (60 lesions each) were analyzed. Comparison of dermoscopy characters was done among PR, GP, and PLC in pairs using chi-square test and a P-value of less than .05 was considered significant. Most common background color in PR (86.7%) and PLC (96.7%) was yellow to yellow-orange and in GP was dull red to pink (70%). Vessels were visualized in all lesions of GP and most characteristic pattern was regular (93.3%), dotted vessels (95%). In PR 63.3% lesions had dotted vessels mostly in a patchy distribution (56.7%). Most prominent scale color in PR was yellow-white (88.3%) and in GP was white-gray (80%). In PLC varying colors were seen, most prominent being brown (53.3%). Characteristic findings seen only in PLC were hypopigmented areas (13.3%), brown dots and globules (53.3%) and orange-yellow structureless areas (61.7%) GP, PR, and PLC reveal specific dermoscopic findings that can help in differentiating them. Further, the known dermoscopic criteria for GP, PR, and PLC also apply for dark skin phototypes.