Clinical features of adult-onset ankylosing spondylitis in Korean patients: patients with peripheral joint disease (PJD) have less severe spinal disease course than those without PJD

Objective. We investigated the clinical features of Korean patients with adult-onset ankylosing spondylitis (AAS) and examined the differences between AAS patients with and without peripheral joint disease (PJD). Methods. We studied 67 consecutive patients with primary AAS who visited the rheumatology clinic of a tertiary referral hospital. All patients experienced joint symptoms after the age of 15 and fulfilled the modified New York criteria for ankylosing spondylitis. Hips and shoulders were not considered as peripheral joints. Results. The male-to-female ratio was 8.6:1.0. Mean age at disease onset was 22.3 +/- 5.5 (mean +/- s.d.) yr and disease duration was 10.8 +/- 8.0 yr. Spinal symptoms were the first manifestations in 80.6% of patients. During the disease course, hip, shoulder and peripheral joint involvement were found in about 60% of patients. In patients with PJD, the most commonly affected joints were the knees and ankles. The pattern of PJD, in most cases, was asymmetrical and mono/oligoarticular. AAS patients with PJD had fewer spinal symptoms than those without PJD as a presenting feature (71.8 vs 92.9%, P = 0.035). The modified Schober test showed greater increments in patients with PJD (4.9 +/- 2.4 vs 3.0 +/- 2.4 cm, P = 0.002). Forced vital capacity was better in patients with PJD (79.0 +/- 11.4 vs 70.8 +/- 15.5% of predicted value, P = 0.016). Totally ankylosed sacroiliitis, spinal squaring and syndesmophytes on radiographs were less common in the patients with PJD than in those without PJD (33.3 vs 64.2%, P = 0.012; 20.5 vs 67.9%, P = 0.000; and 38.5 vs 71.4%, P = 0.008, respectively). Conclusion. Peripheral joints as well as shoulder and hip joints were more frequently involved during the disease course in Korean AAS patients compared with earlier reports in Caucasians. The general joint involvement pattern of PJD was similar to patterns reported previously. Our data suggest that, clinically and radiographically, AAS patients with PJD have a less severe spinal disease course than those without PJD.