An 86-year-old woman with end-stage kidney disease on dialysis presented with new-onset jaw pain, dysphagia, and a right submandibular mass. The case revealed Staphylococcus aureus infection of a carotid artery pseudoaneurysm with concurrent septic arthritis and an incidental atypical lipomatous tumor.
Imaging showed a 14-mm pseudoaneurysm in the distal right common carotid artery, with extensive surrounding edema. Computed tomography angiography revealed wall thickening and inflammation involving the common, internal, and external carotid arteries. The patient also had a large, firm, non-tender mass in the right thigh and new right knee pain. Arthrocentesis yielded synovial fluid with 53,000 nucleated cells/μL (93% neutrophils), raising concern for septic arthritis. Blood cultures were obtained, and empirical treatment with vancomycin and ceftriaxone was initiated.
Imaging on Admission
Radiographs, CT, ultrasound, and MRA revealed a thigh mass and right carotid pseudoaneurysm.
Carotid Artery Specimen
Stains show abscess, inflammation, and gram-positive cocci.
Thigh Mass Imaging and Pathology
MRI and tissue studies confirm atypical lipomatous tumor with MDM2 amplification.
Computed tomography angiography showed the pseudoaneurysm had increased in size compared with prior imaging. Vascular surgery was performed using a cryopreserved femoral-artery graft due to vessel size mismatch. Pathologic analysis confirmed abscess formation and gram-positive cocci in the arterial wall. Cultures grew methicillin-resistant S. aureus. The patient received six weeks of intravenous vancomycin during dialysis. Follow-up ultrasonography showed a stable bypass graft with complete resolution of symptoms.
Orthopedic evaluation of the thigh mass revealed radiologic growth over 10 years. Magnetic resonance imaging demonstrated septated internal architecture and T2 signal variability. Marginal excision was performed. Histopathology showed adipocytes with nuclear atypia and fibrous septa. Fluorescence in situ hybridization confirmed MDM2 amplification, establishing the diagnosis of an atypical lipomatous tumor.
“The cause of the pseudoaneurysm was most likely infection. The mechanism of infection could be direct extension, perhaps related to the patent foramen ovale or the brachiocephalic arteriovenous fistula, although she had no previous trauma or skin puncture, evidence of peritonsillar abscess or odontogenic infection, or hematogenous seeding,” noted Christopher J. Kwolek, MD. Surgical management was successful, and the patient returned to full activity following both procedures.
She lived independently for several years until dying peacefully from COVID-19–related illness 5 years later.
Full disclosures can be found in the case report.