Hyperuricemia is an independent risk factor for psoriatic arthritis in psoriatic patients

Psoriatic arthritis (PsA) is a spondyloarthritic condition mainly seen in patients with psoriasis. Psoriatic patients with plaques on the scalp, gluteal fold or nail lesions are known to develop PsA more frequently, but other markers for PsA have not yet been identified. To determine which psoriatic patients are at greatest risk of developing PsA, psoriasis vulgaris (PsV) patients who visited the Department of Dermatology, Fukuoka University Hospital in 2015 were enrolled. Patients with and without PsA were statistically compared with respect to age, sex, age at onset, body mass index (BMI), smoking and drinking habits, familial history of psoriasis and comorbidities. Of 331 patients (237 men, 94 women), 55 had PsA (17%; 39 men, 16 women). PsA patients had significantly higher frequencies of nail lesions (PsA vs PsV-only, 62% vs 29%; P < 0.0001) and hyperuricemia (PsA vs PsV-only, 22% vs 9%; P = 0.01). These were confirmed as independent risk factors for PsA by logistic regression analysis, with odds ratios of 5.05 for nail lesions (P < 0.0001) and 4.18 for hyperuricemia (P < 0.01). There was no difference in age at onset, sex, BMI and incidence of diabetes mellitus, hypertension or dyslipidemia. Hyperuricemia is also known to be more frequent in psoriatic subjects than the normal population. Uric acid crystals are a strong stimulator of innate immunity. Considering that none of our cohort had gouty arthritis, hyperuricemia may increase uric acid crystallization in and around joints, thereby inducing PsA in psoriatic subjects. Hyperuricemia appears to be an independent risk factor for PsA.