Dermoscopy to Differentiate Guttate Psoriasis from Pityriasis Rosea—a Mimicker

Abstract

Background: Guttate psoriasis (GP) and pityriasis rosea (PR) are a part of papulosquamous disorders that have very similar clinical features and often require histopathology to confirm the diagnosis. Dermoscopy has emerged as a noninvasive, cost-effective technique that can aid in the diagnosis of inflammatory skin diseases like GP and PR. Objective: To study and compare the dermoscopic features of GP and PR. Methods: Twenty consecutive patients each with GP or PR were enrolled in the study. The diagnoses of GP and PR were made clinically and on histopathology. Dermoscopic images were taken of the representative lesions from each patient using a manual dermoscope attached to a digital camera after applying ultrasound gel. Vascular morphology, vascular arrangement, background color, along with color and distribution of scales were noted in each case. Statistical analysis was done using chi-square test to determine the significance of findings in both groups. Results: The combination of a bright red background with dotted vessels in uniform diffuse distribution with diffuse white scales was highly specific for the diagnosis of GP. Lesions of PR showed a red background with dotted blood vessels in nonspecific distribution. Scales were either white in color or brown pigmented with patchy distribution. Brown pigmentation and brown dots were additional findings in cases of PR. Conclusion: Combinations of dermoscopic patterns can aid in the diagnosis of GP and PR in the majority of the cases.