Chapter 28: Rashes & Skin Lesions Assessment

Rashes & Skin Lesions Assessment begins by classifying dermatologic problems through various mechanisms, including inflammatory, infectious, immunologic, and environmental factors, stressing the importance of a systematic history and physical examination. The text details the essential morphologic criteria for identifying lesions, distinguishing between primary lesions—such as macules, patches, papules, plaques, nodules, wheals, vesicles, bullae, and pustules—and secondary lesions like crusts, scales, excoriations, fissures, and lichenification. Diagnostic reasoning is enhanced by analyzing lesion distribution (localized, regional, generalized) and configuration (annular, zosteriform, linear, or iris/target shapes), as well as evaluating associated symptoms like pruritus, pain, and fever. The chapter outlines critical diagnostic studies used to confirm etiologies, including diascopy, dermoscopy, Wood's light examination, potassium hydroxide (KOH) preparation for fungal elements, Tzanck smears for herpes viruses, and bacterial or viral cultures, alongside biopsy techniques. A significant portion of the text is dedicated to the differential diagnosis of common skin conditions, categorized into follicular eruptions (acne vulgaris, rosacea), infectious eruptions (impetigo, folliculitis), and viral exanthems (erythema infectiosum, measles, rubella, roseola). It further explores papulosquamous eruptions like pityriasis rosea and psoriasis, fungal infections such as tinea and candidiasis, and allergic or inflammatory reactions including atopic dermatitis (eczema), contact dermatitis, urticaria, and erythema multiforme. Finally, the chapter addresses the identification of neoplastic eruptions, providing key characteristics for recognizing malignant melanoma, basal cell carcinoma, and squamous cell carcinoma to facilitate early intervention.