Non-Radiographic Axial Spondyloarthritis Presenting with Anterior Chest Wall Pain without Inflammatory Back Pain in an HLA-B27-Negative Young Man: A Case Report Highlighting Diagnostic Challenges.

Background: Non-radiographic axial spondyloarthritis (nr-axSpA) may present with heterogeneous and misleading clinical features, particularly when inflammatory back pain is absent and HLA-B27 is negative. Such presentations can delay recognition and make classification frameworks difficult to apply in routine diagnosis. Case Presentation: We report a 22-year-old Syrian HLA-B27-negative male who initially presented with mild anterior chest wall pain that was clinically interpreted as mechanical and resolved with nonsteroidal anti-inflammatory drugs. Eight months later, he developed a generalized inflammatory flare characterized by severe right hip pain, limping, recurrent anterior chest wall pain, and sacroiliac tenderness, without inflammatory back pain, morning stiffness, or axial rigidity at any stage of follow-up. Inflammatory markers were elevated, while autoimmune and infectious workup was negative. Baseline chest radiography showed no evident cardiopulmonary abnormality or rib osseous lesion, and pelvic radiography showed no definite radiographic sacroiliitis. Magnetic resonance imaging of the sacroiliac joints demonstrated unilateral active sacroiliitis without erosive or destructive change, supporting a diagnosis of nr-axSpA. Serial radiography and computed tomography over 12 months showed no structural progression. The anterior chest wall and hip symptoms were clinically important but not independently image-proven inflammatory lesions. Initial treatment with nonsteroidal anti-inflammatory drugs, low-dose corticosteroids, and conventional synthetic disease-modifying antirheumatic drugs resulted in partial improvement. Anti-tumor necrosis factor therapy was delayed due to access limitations; after subcutaneous golimumab initiation, the patient achieved rapid clinical improvement and sustained remission. Conclusion: This case illustrates the diagnostic value of MRI in an atypical nr-axSpA presentation characterized by HLA-B27 negativity and persistent absence of inflammatory back pain. When conventional imaging is non-diagnostic, MRI can provide important objective evidence, while clinically suspected anterior chest wall and hip manifestations should be distinguished from independently image-confirmed inflammatory lesions.