Different clinical features in patients with ankylosing spondylitis from southern and northern China

Aims: To describe clinical features of patients with ankylosing spondylitis (AS) from southern and northern China, and investigate the effects of onset age, gender and regional differences on disease phenotype. Methods: Totally 113 AS patients from southern China and 121 AS patients from northern China were analyzed retrospectively. Results: In southern and northern groups, low back pain was more frequent among initial symptoms (54.9% vs. 7.7%; 52.4% vs. 11.4%), while peripheral arthritis (15.7% vs. 35.9%; 22.2% vs. 68.6%) was less common in male adult AS (AAS) than in male juvenile AS (JAS) patients, respectively. Compared to those in the northern group, diagnostic delay was longer (7.3 vs. 3.5 years) and the prevalence of human leukocyte antigen (HLA)-B27 was higher in the southern group (96.5% vs. 83.5%). Sacroiliitis grade 2 was more frequent (51.3% vs. 36.4%), while sacroiliitis grade 3 (32.7% vs. 53.7%), buttock pain (5.3% vs. 13.2%), knee (20.4% vs. 33.1%) and ankle (3.5% vs. 11.6%) arthritis were less frequent in the southern group. Diagnostic delay of southern JAS was longer than that of northern JAS regardless of gender. Both sacroiliitis grade 3 and peripheral arthritis were less frequent in southern male JAS than in northern male JAS. Diagnostic delay was longer, sacroiliitis grade 2 was more frequent, while sacroiliitis grade 3 was less frequent in southern male AAS than those in northern male AAS. Conclusion: Significant diagnostic delay and higher prevalence of HLA-B27 were found in southern AS patients. The prevalence of buttock pain and peripheral arthritis at disease onset in northern AS was more frequent than in southern AS patients.