The concept of psoriasis as a systemic inflammation: implications for disease management

Psoriasis is a systemic, immune-mediated disorder, characterized by inflammatory skin and joint manifestations. A range of co-morbidities is associated with psoriasis, including metabolic diseases, such as diabetes, and psychological disorders. Although the systemic nature of psoriasis often remains unrecognized, the inflammatory processes involved may be associated with the development of co-morbidities, which, themselves, have a significant impact on the patient's health and quality of life. The relative risks of myocardial infarction (MI) and stroke are increased in patients with psoriasis compared with the general population. These are especially seen in younger patients with more severe disease, and are believed to contribute to the 3- to 4-year reduction in life expectancy among patients with severe psoriasis. The recent results of large studies indicate that the increased cardiovascular (CV) risk is at least partially attributable to psoriasis and independent of the presence of metabolic co-morbidities. The possible interplay between psoriasis and CV disease is complex. Metabolic diseases such as obesity and diabetes have overlapping genetic predispositions with psoriasis. Both conditions are likely to also interact at a functional level because obesity and the up-regulation of pro-inflammatory mediators in psoriasis appear to influence adipocyte homoeostasis, inducing non-professional immune functions. This may perpetuate psoriatic inflammation, displaying similarities to the immunopathogenesis of atherosclerosis. Finally, the disturbed adipokine profile and inflammation associated with psoriasis enhances insulin resistance, causing subsequent endothelial dysfunction, atherosclerosis and eventual coronary events. The differential contribution of psoriasis and uncontrolled classical CV risk factors to the increased CV risk seen in psoriasis patients is not clear. Successful treatment with methotrexate appears to lower the rates of MI in patients with psoriasis. Tumour necrosis factor-a (TNF-a) inhibitors are known to counteract insulin resistance and emerging studies demonstrate an even higher protective effect of TNF-a antagonist therapy against the development of diabetes or CV co-morbidities in patients. The recent data reviewed here indicate a role for earlier and more appropriate treatment of psoriasis with drugs such as TNF-a antagonists. Such an approach has the potential to significantly improve patient outcomes through the treatment of psoriasis itself and possibly also in protection against co-morbidities.