Psoriasis and psoriatic arthritis: immunological aspects and therapeutic guidelines.

Psoriasis is an inflammatory skin disease that affects 1-3% of the European population. Chronic plaque psoriasis, the commonest form of the condition - affecting the majority of patients - usually manifests as red, heavily scaled plaques on elbows, knees, scalp and lower back, but any skin surface may be affected. Psoriasis is associated with an inflammatory sero-negative arthritis, namely "psoriatic arthritis", in approximately 15%of patients with psoriasis and occurs more commonly in people with inflammatory bowel disease such as patients with Crohn's disease. Several studies have demonstrated the role of genetic predisposition, innate and adaptive immunity in the pathogenesis of psoriasis. There is considerable evidence that innate immunity and specifically a dysregulation of the innate immune response is central to the development of psoriasis. The role of TNFalpha is particularly intriguing. The evidence includes further observations that a variety of anti-TNF approaches such as monoclonal antibodies and fusion proteins of soluble TNF receptors are effective therapies both in psoriasis and psoriatic arthritis. In this review, in addition to pathogenetic aspects, some preliminary guidelines for the use of anti-TNFalpha therapy in patients with psoriasis and psoriatic arthritis will be discussed.