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 Staphylococcus aureus (MRSA)-positive septic arthritis in the SCJ, coupled with its resemblance to mediastinal conditions and a history of multiple injections, presents a rare and complex clinical case that demands thorough evaluation and management.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 Staphylococcus aureus-positive sternoclavicular septic arthritis, mimicking mediastinal malignancy, presents diagnostic challenges. Successful management involves tailored strategies, interdisciplinary collaboration, and consideration of IV drug injections.