Papulosquamous Skin Rash - Differential Diagnosis Algorithm Erythrematous or violaceous papules & plaques with overlying scale • Psoriasis - Well demarcated plaques, thick silvery scale on elbows & knees. Auspitz sign, Koebner's phenomenon • Lichen Planus - Purple, pruritic, polygonal, planar (flat-topped) papules on wrists/ankles/genitals (especially penis) Wickham's striae, Koebner's phenomenon • Pityriasis Rosea - Oval, tannish-pink or salmon-coloured patches, plaques with scaling border in Christmas tree pattern on trunk, begins with a large lesion patch Herald's atch • Tinea (Ring Worm) - Annular (Ring- shaped) lesion with elevated scaling, red border, central clearing • Secondary Syphilis - Red brown or copper coloured scaling papules and plaques on palms and soles • Discoid Lupus Erythematous - Scarring and/or atrophic red/purple plaques with white adherent scales on sun-exposed area #Papulosquamous #SkinRash #dermatology #Differential #Diagnosis #Algorithm #causes
