Septic arthritis of the sternoclavicular joint accounts for less than 1% of all the cases of septic arthritis. It is frequently associated with predisposing conditions, such as intravenous drug abuse or diabetes. Given the infrequency of the disease, the diagnosis is often delayed.1Serratia marcescens is a Gram-negative enterobacterium associated with a wide range of nosocomial infections.2

We report a case of sternoclavicular joint septic arthritis caused by this enterobacterium. The patient was a 70-year-old man diagnosed with hypertension, type 2 diabetes, dyslipidemia and chronic ischemic heart disease in the form of unstable angina, with percutaneous revascularization of anterior descending and circumflex arteries. On admission to the hospital for unstable angina, catheterization revealed no evidence of new coronary lesions. On the third day of his hospital stay, he experienced chills, pain in his left shoulder and dysphagia. On clinical examination, the only notable findings were an arterial blood pressure of 150/76mmHg, body temperature of 38°C, edema and erythema in left sternoclavicular joint, and pain on moving his left arm. The analytical findings included a hemoglobin level of 11.2g/dL and leukocyte count at 3600/mm3, with 7.5% lymphocytes and 85.8% neutrophils, platelet count of 84,000/mm3 and C-reactive protein at 325mg/L. Blood cultures revealed the presence of Serratia marcescens sensitive to quinolones, carbapenems, aminoglycosides and third-generation cephalosporins. Computed tomography of his neck and chest (Fig. 1) confirmed the presence of an infectious process in the sternoclavicular joint, with no signs of local complications. The results of an otorhinolaryngological examination were normal. It was not possible to obtain a sample of joint fluid. There was no evidence of endocarditis on transthoracic echocardiography. He was treated with 1g/day of intravenous ertapenem for 4 weeks, followed by a 2-week regimen of oral ciprofloxacin (500mg/12h). In view of the favorable clinical response and analytical findings, surgical treatment was ruled out.

Fig. 1.

Augmentation of soft tissue and obliteration of fat planes associated with the inflammatory-infectious process in left sternoclavicular joint (arrows).

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Septic arthritis of the sternoclavicular joint is an uncommon disease3 in both immunocompetent and immunocompromised individuals.4 The risk factors are diabetes mellitus, rheumatoid arthritis, intravenous drug abuse, neoplastic diseases, chronic kidney disease, human immunodeficiency virus infection, cirrhosis, local trauma and central line infections.4 The fact that our patient was a diabetic and, moreover, had undergone cardiac catheterization is important. Staphylococcus aureus is the most common causative agent.5 Until now, there has been only one case attributed to infection by Serratia marcescens in the medical literature.6 The most common mechanism of infection is bacteremia.7 Patients may complain for days or even months of pain in shoulders, neck or chest, with limited arm mobility, associated with fever. The clinical picture in our patient was similar to those reported by other authors. However, we consider that the dysphagia was related to extrinsic compression of the esophagus.1 Joint inflammation and erythema can also be present. Sternoclavicular arthritis is generally unilateral, and is right-sided in 60% of the cases. Bacteremia is found in 62% of the patients. Computed tomography is the initial imaging technique that can identify bone involvement and detect retrosternal dissemination. The most serious complication is mediastinitis, which occurs in 15% of the cases.7 The initial therapeutic approach includes prolonged antibiotic therapy when there are no complications. However, in the presence of extensive osteomyelitis, abscesses or mediastinitis, surgical treatment is recommended.8 Debridement is the surgical technique associated with the lowest incidence of complications.9 In conclusion, septic arthritis of the sternoclavicular joint is uncommon, especially that caused by enterobacteria. However, it is potentially disabling and fatal, and should be suspected in any condition that affects the sternoclavicular region.