Septic acromioclavicular arthritis in a patient with diabetes mellitus.

A 44-year-old diabetic man with isolated septic arthritis of the left acromioclavicular joint (A-C) caused by Staphylococcus aureus is described. He was admitted to the Department of Rheumatology with clinical symptoms of left shoulder arthritis and fever. Laboratory findings showed leukocytosis, elevated levels of erythrocyte sedimentation rate and C-reactive protein, all indicating septic arthritis. Blood culture was positive for Staphylococcus aureus. Left A-C joint x-ray and ultrasonography, and whole body scintigraphy with 99 mTc radiolabeled autologous leukocytes pointed to septic arthritis of the A-C joint. The patient was treated for six weeks with antibiotics successfully. Infection of the A-C joint is uncommon, even in conditions such as immunodeficiency, renal dialysis and intravenous drug abuse which are associated with unusual joint infections, and can be differentiated from shoulder joint infection, by maximal tenderness over the A-C joint on examination, and findings of A-C joint widening, effusion, and bony erosions on imaging studies.