Medical backgrounder: psoriasis.

Psoriasis is a chronic skin disorder that affects approximately 2% of the US and European populations. Psoriatic lesions are extremely characteristic of the disease, which allows for simple diagnosis. A clear understanding of the pathogenesis of psoriasis does not yet exist. Hyperproliferation of keratinocytes is a further characteristic feature. Studies have depicted that the epidermal cell cycle of psoriatic lesions is shortened by approximately eight-fold more than normal. The lesions are classified as erythrosquamous, due to the erythema which develops asa result of involvement of the vasculature, and the involvement of the epidermis with scale formation. The diagnosis of psoriasis can usually be established on clinical grounds. If the clinician is in doubt, a small cutaneous punch biopsy and subsequent histopathological examination can be performed. There are multiple therapeutic options for psoriasis. First-line therapy for patients with moderate to severe psoriasis is the application of topical agents, followed by phototherapy (UVB) for more extensive disease. If extensive disease does not respond to UVB, second-line agents include psoralen plus UVA (PUVA), methotrexate, cyclosporine or other systemic agents, including novel biologic therapies. New psoriasis treatment regimens have been developed and include combination, rotational and sequential therapy.