Septic arthritis of the sternoclavicular joint and osteomyelitis of the proximal clavicle caused by prevotella melaninogenicus: a case with several features delaying diagnosis.

A 50-year-old woman with noninsulin-dependent diabetes and cirrhosis of the liver from hepatitis-B infection presented with right-sided neck and severe shoulder pain. Minimal tenderness and swelling of the right sternoclavicular joint were noted. After 8 days, extensive studies, and several attempts at therapy to relieve the shoulder pain, the right sternoclavicular joint had become more swollen, extremely tender, warm, and erythematous. An arthrotomy of the right sternoclavicular joint revealed pyoarthosis of the joint and osteomyelitis of the adjacent clavicle. Both tissue and blood cultures grew Prevotella melaninogenicus. A site of origin for the infection was never found. The patient had an uneventful recovery after treatment with open drainage and parenteral antibiotics. Although this anaerobic organism is known to cause infection at other joint sites, this seems to be the first report of infection of the sternoclavicular joint and proximal clavicle by Prevotella melaninogenicus.This case illustrates the following: 1) neck and shoulder pain may be the presenting symptoms of occult septic arthritis of the sternoclavicular joint, 2) clinical signs of infection, such as fever and leukocytosis, may be absent in the setting of anaerobic joint infections, 3) an arthrotomy should be performed as soon as an infection of the sternoclavicular joint is suspected, 4) anaerobic as well as aerobic cultures should be taken when evaluating septic arthritis 5) 2 or more weeks may be required for identification of an anaerobic organism, such as Prevotella melaninogenicus.