Diagnostic challenges in acromioclavicular septic arthritis

A 69-year-old man with Klinefelter's syndrome presented with a painful shoulder and staphylococcal sepsis. He received intravenous antibiotics while investigations were performed to locate the source of infection. MRI demonstrated infection in the acromioclavicular joint (ACJ). The patient clinically improved and a further 5 weeks of oral antibiotics were given. He remained asymptomatic at 2-year follow-up. Although ACJ septic arthritis is rare, independent of immune-competent status, a high index of suspicion is essential for prompt diagnosis. The condition presents additional diagnostic challenges due to unfamiliarity, the challenges of interpreting imaging, desire for radiological guided arthrocentesis and low volume aspirates. Overcoming these pitfalls is essential to avoid significant morbidity and mortality.