Patterns and pitfalls: Dermoscopic differentiation of early-stage mycosis fungoides, atopic dermatitis, and psoriasis.

Abstract

Mycosis fungoides (MF), psoriasis (Pso), and atopic dermatitis (AD) may present with overlapping clinical features, which may lead to delayed diagnosis. Dermoscopy, including ultraviolet (UV) mode, can help distinguish disease-specific patterns. To compare dermoscopic and UV features of early-stage MF, Pso, and AD. In this prospective cohort study, 159 patients (MF: 55, Pso: 53, AD: 51) were examined with dermoscopy and UV mode. Vascular patterns, scale features, background color, structureless areas, and vessel density per mm² were analyzed. Group differences were assessed with chi-square/Fisher's exact tests or ANOVA/Welch ANOVA, using Bonferroni/Games-Howell corrections. MF showed linear and spermatozoa-like vessels, scaling along skin furrows, focal structureless areas, and the lowest vessel density. Pso was defined by uniformly distributed dotted vessels on a bright-red background with diffuse scaling and the highest vessel density. AD showed mainly dotted vessels with additional linear vessels, along with yellow-orange scale, ulceration, dystrophic hairs, and intermediate vessel density. UV imaging improved visualization of structureless areas and scaling edges. Single-center design, modest sample size, and restriction to early stages may limit generalizability. Dermoscopy with UV mode shows distinct features in MF, Pso, and AD. This approach may support early, noninvasive differentiation.