Spondylitis is the most common pattern of psoriatic arthritis in Korea.

We assessed the prevalence and clinical features of psoriatic arthritis (PsA) in Korean patients with psoriasis. The prevalence of PsA in patients with psoriasis was 9%. Patients with PsA were older and had a longer duration of skin disease than those with psoriasis alone (median age, 40 vs 35 years, P = 0.03, and 15.3 vs 11.7 years, P = 0.04, respectively). Spondylitis was the most common pattern of PsA (50%). Nail change, dactylitis, and enthesopathy were observed in 36%, 15.4%, and 15.6% of patients with PsA, respectively. Increased erythrocyte sedimentation rate (ESR), antinuclear antibody, and radiological sacroiliitis were more frequent in patients with PsA than in those with uncomplicated psoriasis (25.8% vs 10.3%, P = 0.04; 37.9% vs 16.7%, P = 0.02; and 37.8% vs 1.1%, P < 0.01, respectively). The onset ages of psoriasis and arthritis in the spondylitis group were significantly lower than those in the non-spondylitis group (median age, 21.5 vs 31 years, P = 0.03, and 28.5 vs 43.5 years, P = 0.01, respectively). HLA-B27 was prevalent in 8% of patients with PsA.