Prevalence of axial spondyloarthritis in Behcet's syndrome

Purpose: Although Behçet's syndrome (BS) and spondyloarthropathies (SpA) have distinct features, both can present with uveitis, enthesitis, inflammatory bowel disease, arthritis. Both conditions are also strongly linked to MHC class I, genome wide association studies have revealed similar pathways. This study aimed to determine the prevalence of axial SpA (axSpA) in BS patients using the Assessment of SpondyloArthritis International Society (ASAS) classification criteria. Methods: The study included 296 BS patients under 45 who met International Study Group criteria. ASAS classification criteria for axSpA were applied to those with chronic back pain, SpA features were assessed in individuals with current or past pain. HLA-B27, C-reactive protein testing, MRI of the sacroiliac joints, plain radiography were performed. Inflammatory back pain was evaluated per ASAS criteria, two radiologists reviewed the imaging. A one-sample t-test compared the prevalence of axSpA in BS to the general population's prevalence of 1.4%. Results: Of the 296 patients, 88 (29.7%) reported chronic lower back pain, with 43 (48.8%) inflammatory pain. Fifteen patients (5%) met the ASAS criteria for axSpA, including one of eight with a history of chronic back pain. In total, 16 axSpA patients were identified: 4 with radiographic axSpA, 5 with non-radiographic axSpA, 7 diagnosed clinically. Conclusion: The prevalence of axSpA in BS was 5% per ASAS criteria, with no increase compared to the general population. Many SpA features can appear in BS, suggesting it may mimic SpA (and vice versa). However, major organ involvements like posterior uveitis, vascular or neurological issues can differentiate the two diseases.