Background Although axial spondyloarthritis (axSpA) is a chronic inflammatory disease primarily affecting the axial spine, some patients may also present with peripheral arthritis. There is limited research on the clinical characteristics and treatment options for axSpA patients with peripheral arthritis, both domestically and internationally, leading to frequent misdiagnosis and mistreatment.

Objective To compare the clinical characteristics and treatment options between two groups of axSpA patients with or without peripheral arthritis, in order to assist clinicians in early detection and identification.

Methods This was a retrospective study. axSpA patients who admitted to Chinese PLA General Hospital firstly from January 2016 to December 2022 were consecutively included. Patients were divided into the group with peripheral arthritis and the group without peripheral arthritis. A propensity score matching was performed to balance the baseline characteristics between the two groups using the visit time as a matching factor in a 1:3 ratio. After matching, 456 patients with axSpA (114 with peripheral arthritis and 342 without peripheral arthritis) were included in the analysis. The clinical characteristics and differences in treatment choices between the two groups were compared.

Results Of the 456 patients with axSpA, there were 357 males and 99 females with a median age of 30.0 (IQR: 25.0 - 36.5) years. Compared to axSpA patients without peripheral arthritis, axSpA patients with peripheral arthritis had a later onset of disease (MIQR: 23.0 18.6 - 31.7 years vs 21.5 17.0 - 27.0 years, P=0.022), a shorter disease duration (MIQR: 5.7 1.7 - 10.5 years vs 7.7 3.5 - 11.4 years, P=0.024), a lower body mass index (BMI) (MIQR: 22.3 19.6 - 25.3 kg/m² vs 23.6 20.7 - 25.8 kg/m², P=0.01), a lower smoking rate (10.5% 12/114 vs 28.4% 97/342, P<0.001), and a higher prevalence of enthesitis and dactylitis (P<0.05 for both). Moreover, axSpA patients with peripheral arthritis had higher erythrocyte sedimentation rate and C-reactive protein (CRP) (P<0.05 for both). In terms of treatment, patients with peripheral arthritis had less usage of traditional Chinese medicine (44.7% 51/114 vs 59.9% 205/342, P=0.005), while higher usage of conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) (79.8% 91/114 vs 59.9% 205/342, P<0.001), biologic disease-modifying antirheumatic drugs (bDMARDs) (40.4% 46/114 vs 21.3% 73/342, P<0.001), and glucocorticoids (9.6% 11/114 vs 0.6% 2/342, P<0.001), and were more often treated with a combination of csDMARDs and bDMARDs (30.7% 35/114 vs 9.4% 32/342, P<0.001) or two or more csDMARDs (43.0% 49/114 vs 9.9% 34/342, P < 0.001). The results of the logistic regression analysis of factors indicated that younger age at onset (OR=0.967, 95% CI: 0.942-0.992, P=0.011), smoking (OR=1.745, 95% CI: 1.030-2.955, P=0.038), presence of uveitis (OR=2.169, 95% CI: 1.025-4.592, P=0.043) / psoriasis (OR=20.838, 95% CI: 2.340-185.560, P=0.006), peripheral arthritis (OR=2.482, 95% CI: 1.423-4.332, P=0.001), or elevated CRP levels (OR=1.011, 95% CI: 1.003-1.020, P=0.011) were associated with the use of bDMARDs in axSpA patients.

Conclusion Patients with peripheral arthritis, despite having a later onset and shorter disease duration, often require multiple drug therapies due to the presence of more enthesitis, dactylitis, and higher inflammatory markers.