Case Presentation: A 38-year-old previously healthy male presented with 2 weeks of progressive right sternoclavicular (SC) swelling, shoulder pain, fevers, and night sweats. He denied trauma, injection drug use, or recent illness. CT showed right SC joint distension and cortical irregularity with overlying muscular swelling and subcutaneous soft tissue infiltration. MRI showed osteomyelitis of the right clavicular head and a 3.6 cm abscess of the right pectoralis major. Joint aspiration yielded < 1 mL of bloody fluid, which grew pansensitive methicillin-susceptible Staphylococcus aureus (MSSA). The patient initially received vancomycin and piperacillin-tazobactam, which was narrowed to cefazolin. Blood cultures remained negative. However, given minimal clinical improvement, irrigation and debridement of the SC joint and pectoralis major was performed. A small anterior mitral valve echodensity was noted on TTE concerning for infectious endocarditis. To avoid prolonged hospital stay for long-term IV antibiotics, the patient was transitioned to dalbavancin 1,500 mg on the day of discharge with repeat doses scheduled outpatient for 1 week and 6 weeks later. The patient was able to return to work two days post discharge and had significant improvement in range of motion, pain, and swelling at 8 week follow-up visit.
Discussion: SC joint septic arthritis accounts for < 1% of septic arthritis cases. Though frequently associated with intravenous drug use, diabetes, or immunosuppression, it can present in healthy adults. SC joint septic arthritis poses a diagnostic and therapeutic challenge due to its rarity, insidious onset, and proximity to vital structures. In this case, despite the absence of traditional risk factors, MSSA caused extensive joint, bone, and soft tissue involvement. Dalbavancin’s long half-life and favorable safety profile allowed for an effective outpatient regimen that replaced traditional 6-week IV antibiotic therapy while mitigating hospitalization duration, central venous access, and associated risks. Published adult septic arthritis cohorts report average hospital stays of ~7-13 days in a U.S. dataset and ~16 days in a European study, often longer in cases requiring surgical debridement. In contrast, this patient’s hospital stay was limited to five days, reflecting the value of transitioning early to long-acting outpatient therapy. This aligns with recent literature supporting dalbavancin’s role in serious MSSA infections, including osteomyelitis and endovascular involvement, as well as a recent randomized clinical trial which demonstrated non-inferiority compared to conventional regimens for S. aureus bacteremia.
Conclusions: This case highlights the importance of early recognition of rare joint infections, especially in immunocompetent adults, and presents dalbavancin as an option for deep tissue MSSA infections. It also highlights ways in which dalbavancin treatment can alleviate the logistical burden long-term IV antibiotics traditionally places on patients and decrease hospital length of stay.