Chronic non-bacterial osteitis presenting with upper limb deep vein thrombosis: diagnostic clues and therapeutic considerations.

A 40-yr-old Scandinavian man with a 10-yr history of palmoplantar pustulosis presented with left upper limb swelling and was diagnosed with a deep vein thrombosis. Imaging revealed subclavian vein compression due to marked clavicular hyperostosis. The patient reported longstanding sternoclavicular pain, inflammatory back pain, and electronic health records review showed persistently elevated inflammatory markers. CT demonstrated extensive cortical overgrowth of the clavicle consistent with chronic non-bacterial osteitis (CNO), alongside thoracic syndesmophytes suggestive of axial spondyloarthritis-like involvement. Long-term anticoagulation was initiated, and rheumatology assessment confirmed CNO. TNF inhibition therapy was started to control the inflammatory symptoms. This case highlights a rare but serious complication of CNO: thoracic outlet obstruction with secondary thrombosis from progressive bone overgrowth. Earlier recognition might have prevented irreversible structural and vascular sequelae. It also underscores current uncertainties in CNO management, including whether treatment can prevent hyperostosis, how to identify high-risk patients, and the optimal duration of treatment.