The role of clinical examination and dermoscopy in the differential diagnosis of psoriasis and dermatitis in different locations. A literature review

Dermoscopy has emerged as a valuable tool in the differential diagnosis of various inflammatory conditions with similar clinical features, such as psoriasis and dermatitis. In this postgraduate thesis, a literature review and a comprehensive presentation of the clinical and dermoscopic characteristics of psoriasis and dermatitis in different locations will be conducted, with the ultimate goal of achieving timely and accurate diagnosis of these two conditions. Initially, the clinical features of psoriasis are presented, with the most common being erythematous, well-demarcated plaques covered by silvery scales, which detach from the skin. Next, the clinical appearance of dermatitis (eczema) is described, characterized by clusters of vesicles with varying degrees of exudate and desquamation. Dermoscopically, psoriasis generally presents with characteristics such as the presence of whitish scales, dotted vessels against a light red background, and a regular vascular distribution pattern. In contrast, dermatitis exhibits features including more diffuse patterns, patchy scale distribution, atypical vessels, and yellow crusts. Moreover, specific dermoscopic features may be observed at different sites, such as the brown-orange-yellow dots and globules found in palmoplantar eczema, or the prevalence of signet ring vessels as trichoscopic finding in scalp psoriasis, contrasting with the arborizing red lines and comma vessels noted in seborrheic dermatitis of the scalp. Onychoscopy further provides valuable insights for differentiating between nail psoriasis and atopic dermatitis impacting the nails, where leukonychia and fuzzy lunula are characteristic of the former, while melanonychia, chronic paronychia, and trachyonychia are associated with the latter.