Ankylosing spondylitis following chronic brucellosis: a causal association or separate pathology? A case-based review.

Brucellosis is a widespread zoonotic infection that often follows a chronic course and may involve the osteoarticular system. Patients with brucellosis-related musculoskeletal manifestations are frequently evaluated by rheumatologists and may be misdiagnosed with rheumatic diseases, including ankylosing spondylitis. We present the case of a 45-year-old female patient who was diagnosed with osteoarticular brucellosis approximately 20 years ago and was successfully treated with etiotropic therapy. Eighteen years later, she developed back pain that worsened at night and did not improve with rest, accompanied by morning stiffness. Further evaluation revealed negative specific anti-Brucella antibodies, HLA-B27 positivity confirmed by polymerase chain reaction, and magnetic resonance imaging findings supporting the diagnosis of ankylosing spondylitis/axial spondyloarthritis. A literature review including 21 relevant sources was conducted to analyse the diagnostic overlap and possible coexistence of brucellosis and ankylosing spondylitis. The reviewed evidence, together with the clinical course of the present patient, supports the interpretation that ankylosing spondylitis developed as a separate pathological condition rather than as a direct consequence of previously treated brucellosis. This case highlights the importance of careful differential diagnosis between brucellosis-related osteoarticular involvement and axial spondyloarthritis, particularly in patients from brucellosis-endemic regions or with relevant epidemiological exposure.