Systemic therapies for psoriasis: understanding current and newly emerging therapies.

The treatment of moderate to severe psoriasis is a rapidly expanding area. Recent insights into the pathogenesis of this disease as a T-cell mediated process has led to a greater understanding of the mechanisms of action of conventional FDA-approved systemic therapies such as methotrexate, cyclosporine, acitretin, and psoralen with ultraviolet A phototherapy. It has also led to the development of rationally targeted therapies against key components of the immune process critical in the generation of the psoriatic plaque.