DISEASE REVIEW

PSORIASIS

Psoriasis is a chronic inflammatory and proliferative disorder of the skin clinically manifested as well-cir- cumscribed, erythematous papules and plaques cov- ered with silvery scales typically located over the ex- tensor surfaces and scalp. While specific systemic and environmental factors are known to influence the dis- ease, it is unpredictable in its course, and usually pur- sue spontaneously with improvement and exacerba- tions of lesions without discernable cause. Immune system dysfunction in the background of a genetic predisposition is believed to be at the core of the dis- ease process. Psoriasis is a very common disease and affects one to two per cent of the population in all geographic regions

Aetiology and Pathogenesis
Despite being the subject of intensive research over the years, the precise aetiology of psoriasis still remains unknown.

Genetic factors can be implicated on the basis of population surveys, twin studies and analysis of pedi- grees. But the precise mode of inheritance is uncer- tain, thought to be polygenic. The HLA system pro- vides a potential genetic marker. Different groups of psoriatic population showed the following to be sig- nificantly associated with psoriasis: HLA Cw6, B13, B16, and B27.

Provocating factors: A number of factors may pro- voke onset or aggravation of psoriasis. :.

Trauma – All types of trauma can lead to the devel- opment of plaque psoriasis (eg, physical, chemical, surgical, infective, and inflammatory). The develop- ment of psoriatic lesions at a site of injury is known as the Koebner phenomenon.