Psoriasis is a common, chronic immune-mediated skin disease which may also affect the joints.
Psoriasis is characterized by scaly, erythematous (reddened) patches, papules, and plaques which are usually itchy.
The cause of psoriasis is not fully understood. There are two main hypotheses about the process that occurs in the development of the disease. The first considers psoriasis as primarily a disorder of excessive growth and reproduction of skin cells. The problem is simply seen as a fault of the epidermis and its keratinocytes. The second hypothesis sees the disease as being an immune-mediated disorder in which the excessive reproduction of skin cells is secondary to factors produced by the immune system. T cells become active, migrate to the dermis and trigger the release of cytokines which cause inflammation and the rapid production of skin cells.
Typically topical agents are used for mild disease, phototherapy for moderate disease, and systemic agents for severe disease. Topical agents include coal tar, dithranol, corticosteroids like desoximetasone, fluocinonide, vitamin D3 analogues and retinoids are routinely used. The three main traditional systemic treatments are methotrexate, cyclosporine and retinoids.