Psoriasis: Triggering factors and immunopathology

Psoriasis is a chronic skin disorder characterised by erythematous scaly papules. Psoriasis affects 1-3% of the world population. It is a Th 1-mediated T-cell disease associated with genetic and environmental triggering factors. Stress, skin injury, bacterial infection, and certain drugs have been identified as the four major environmental factors of the disease. Psoriasis is linked to the class I and 11 major histocompatibility complex on human chromosome 6. It consists of two distinct disease subtypes (type I and type 11), which differ in age of onset and in the frequency of human leukocyte antigens. Psoriasis is a clinically well-characterised, inflammatory, hyperproliferative skin disease that results partly from chronic dysregulation of the immune response system. Several immunocytes and cytokines are involved in psoriasis pathogenesis. The aim of this review was to summarise the data in the literature concerning several pathogenetic and immunologic aspects of psoriasis.