Dermoscopy in the Diagnosis of Palmoplantar Eczema and Palmoplantar Psoriasis: A Cross-Sectional, Comparative Study from a Tertiary Care Centre in North India

INTRODUCTION: Palmoplantar hyperkeratotic lesions pose a diagnostic difficulty when differentiating clinically between palmoplantar psoriasis (PPP) and palmoplantar eczema (PPE). Dermoscopy can provide valuable clues in reaching the final diagnosis. OBJECTIVES: To identify and compare dermoscopic findings seen in PPP and PPE. METHODS: This was a cross-sectional, comparative study carried out prospectively between March 2019 and June 2020. All adult, consenting patients visiting the dermatology outpatient department who were clinically diagnosed and histopathologically confirmed as PPP and PPE were recruited into two groups. The dermoscopic examination was done, and images were taken from the representative area. The findings were analysed by two dermatologists who were unaware of the diagnosis. The sensitivity, specificity, positive predictive value and negative predictive value of these findings were assessed. RESULT: A total of 81 patients were recruited (39 patients of PPP and 42 patients of PPE). Significant findings seen in psoriatic plaques were the presence of regular vessels (84.6%, P < 0.001), with diffuse scales (87.2%) over a dull red/pink background (69.2%, P < 0.001). Dermoscopy of PPE displayed a significant presence of yellowish scales (76.2%, P < 0.001), with focal (61.9%) or absent vessels (35.7%), brown/orange-brown dots and/or globules (66.7%), yellow/yellow-orange crusts (57.1%) over a yellow/yellow-brown background (88.1%). CONCLUSION: Distribution of vessels, distribution of scales and the colour of scales, presence of brown/orange-brown dots and/or globules, yellow/yellow-orange crust and background colour (dull red vs. yellow/yellow-brown) of the plaques can be useful clues in the diagnosis of PPP and PPE.