The impoant feature of psoriasis is -

psoriasis:-chronic Inflammatory skin disease.Genetic predisposition. Psoriasis susceptibility 1 (PSORS1) is the most impoant susceptibility locus. Clinical features:-1. Classic lesion-Well defined erythematous plaque with a silvery white scales.2. Size varies from pin point papules to plaques.3. The scales are loosely adhered,and on renoval of scales,coherent scaling can be seen as if one scratches a wax candle ( signe de la tache de bougie).4. On complete removal of scales,a red moist membrane ,Bulkeley membrane, seen.5. On fuher scraping,punctate bleeding points are seen.-Auspitz's sign.This occurs due to suprapapillary thinning and capillary dilatation.6. A surrounding ring of hypopigmentation seen ,Woronoff's ring, seen associated with the treatment and implies a good response to treatment impoant features of psoriasis- 1.erythematous scaly plaques covered with loosely adherent silvery scales. 2.auspitz sign 3.koebners phenomenon IADVL textbook of dermatology,page 1032