ABSTRACT
Psoriasis is important because of its frequency, its recurrent nature and its tendency to disable a significant proportion of its victims. Psoriasis is a common, genetically determined, inflammatory skin disorder of unknown cause, which, in its most usual form, is characterized by well-demarcated, raised, red scaling patches that preferentially localize to the extensor surfaces. Psoriasis affects the extensor aspects of the trunk and limbs preferentially. Flexural lesions, which occur in some patients, are most often seen in the major body folds in the elderly, especially in those who are overweight. Psoriasis is a life-long disorder subject to unpredictable remissions and relapses. The commonest variant is hypertrophic lichen planus, in which thickened, mauvish papules, nodules or plaques of irregular shape with a warty or scaling surface develop. Lichen planus appears to be in the general category of autoimmune diseases and patients affected by it have a higher frequency of other autoimmune disorders than a comparable unaffected population.
