MRSA-positive sternoclavicular septic arthritis mimicking mediastinal malignancy in a patient with multiple injection history: a rare case report.

Introduction and importance: Infection of the sternoclavicular joint (SCJ) is exceptionally rare, accounting for less than 1% of bone infections. The presence of methicillin-resistant Case presentation: A 60-year-old male with a complex medical history, including hypertension, diabetes mellitus, hepatitis C, and recurrent cellulitis due to multiple intravenous (IV) and intramuscular injections, presented with drowsiness and a painful, erythematous swelling of the left anterior chest wall. Clinical examination revealed pallor, distended abdomen, and decreased left-sided airway entry. Diagnostic workup showed elevated creatinine, metabolic acidosis, and inflammatory markers. Imaging revealed extensive soft tissue swelling and a mediastinal mass. A core biopsy confirmed severe acute and chronic inflammation, abscess formation, and granulation tissue suggestive of an infectious etiology. CT scans further identified sternoclavicular septic arthritis, a rare diagnosis. Clinical discussion: This case report describes MRSA-positive sternoclavicular septic arthritis in a patient with a history of tramadol and multivitamin injections. Sternoclavicular joint infection is rare, complicating differentiation from mediastinal malignancies. Successful management required embolization, IV antibiotics, and physiotherapy. Conclusion: Methicillin-resistant