Psoriasis and cardiovascular risk: strength in numbers, part II.

The Psoralen plus Ultraviolet-A (PUVA) cohort study has been a tremendous success in determining how a novel treatment (i.e., PUVA) affects the long-term risk of keratinocyte carcinoma. The ability to follow patients from the initial multicenter clinical trial for more than three decades has been a remarkable achievement in dermatoepidemiology. In this issue, Stern and Huibregtse report results from the PUVA follow-up study and conclude that only patients with exceptionally severe psoriasis have an increased overall mortality risk and that there is no significant risk of cardiovascular mortality associated with psoriasis. The results are in contrast to a large and growing body of literature that suggests patients with more severe psoriasis have a clinically significant increased risk of mortality in general and cardiovascular disease in particular. In addition, the authors found no association between severe psoriasis and obesity or between obesity and cardiovascular mortality, despite extensive literature establishing these associations. Basic principles of epidemiological study design may explain these discrepancies. Ultimately, however, randomized clinical trials will be necessary to determine whether severe psoriasis is in fact a "visible killer," as four decades ago (after many years of controversy) hypertension was recognized to be a "silent killer."