Are patients with psoriasis susceptible to the classic risk factors for actinic keratoses?

Background: An increased prevalence of benign solar damage (eg, facial wrinkles) but not neoplastic lesions was observed among patients with psoriasis who were exposed to Dead Sea climatotherapy compared with controls. Objectives: To compare the prevalence of actinic keratosis in psoriatic patients and controls and to assess whether known risk factors behave similarly in both groups. Design: Multicenter cross-sectional study. Setting: Dermatology clinics in 4 participating Israeli hospitals and at a Dead Sea clinic. Participants: Adult subjects (n=460) with plaque-type psoriasis were recruited from the Israel Psoriasis Association (volunteer sample) and from dermatology clinics (convenience sample). The control group (n=738) consisted of nonimmunosuppressed patients attending these clinics for benign conditions unrelated to sun exposure, such as atopic or contact dermatitis. Main Outcome Measures: Prevalence and distribution of actinic keratoses and odds ratios associated with skin, hair, and eye color and propensity or history of sunburn adjusted for age, ethnicity, and sun exposure. Results: Actinic keratoses were observed in 200 controls (27%) and 51 subjects (11%) (P<.001). This increased prevalence occurred in both sexes, participants aged 35 years or older, all ethnic groups, smokers, and nonsmokers. The anatomical distribution of lesions did not substantially differ between subjects and controls. In multivariate analysis, psoriasis conferred a protective effect (odds ratio, < 1), as did dark skin, dark eyes, and a history of severe sunburn in childhood. However, significant interactions were observed between psoriasis and hair color as well as psoriasis and propensity to sunburn, whereby a linear association was observed for controls but not for patients with psoriasis. Conclusions: Psoriasis confers protection against actinic keratosis. Hair color and propensity to sunburn exert differential effects among psoriatic patients and controls.