Septic arthritis of the manubriosternal joint presenting as a chest-wall swelling in an immunocompetent patient

Septic arthritis of the manubriosternal joint is a rare pathology, often mistaken for other disease processes given its location and chest pain symptoms. We present a case of a 58-year-old man presenting with a dull ache in his chest after returning from a holiday. Initially under the care of the physicians locally, he was investigated for respiratory and cardiac causes of chest pain with no findings. Eventually, a lump was noted on examination of the chest prompting further imaging, which confirmed a diagnosis of manubriosternal septic arthritis. He was discussed and referred to tertiary cardiothoracics, who recommended conservative treatment with 6 weeks of antibiotics. To date, there has been a good recovery. We present this case alongside a discussion of the limited literature, in particular highlighting how difficult a diagnosis it is to make but one that surgeons and medics alike should be aware of.