dermatologic disorders
Psoriasis
Diagnosis of Psoriasis
Clinical evaluation Rarely biopsy Diagnosis of psoriasis is most often by clinical appearance and distribution of lesions. Differential diagnosisincludes Seborrheic Dermatitis None Overview of Dermatophytoses (potassium hydroxide wet mount should be done for any scaly plaques, especially if they do not have a classic appearance of eczema or psoriasis) Subacute cutaneous lupus erythematosus (SCLE) None Atopic Dermatitis (Eczema) None Lichen Planus None Allergic contact dermatitis (ACD) None Pityriasis Rosea None Squamous cell carcinoma in situ ( Squamous Cell Carcinoma in Situ , especially when on the trunk; this diagnosis should be considered for isolated plaques that do not respond to usual therapy) Lichen Simplex Chronicus None Secondary syphilis None Biopsy is rarely necessary and may not be diagnostic; however, it may be considered in cases where the clinical findings are not classic. Disease is graded as mild, moderate, or severe based on the body surface area affected and how the lesions affect the patient's quality of life. To be considered mild, usually < 10% of the skin surface should be involved. There are many more complex scoring systems for disease severity (eg, thePsoriasis Area and Severity Index), but these systems are useful mainly in research protocols. 