A 61-year-old Vietnamese male with a past medical history of coronary artery disease, peripheral vascular disease, and abdominal aortic aneurysm underwent an axillary-bifemoral bypass and bilateral lower extremity thromboembolectomy. He was referred to our tertiary care center when his preoperative course was complicated by malaise, productive cough, and weight loss of 5 pounds over 5 weeks. The patient was a smoker and was currently employed as an electronics engineer. He denied night sweats, tuberculosis exposure, foreign travel, or animal contact in the past six months. He did report a cattle field along his route to work.
Abnormal laboratory values were as follows: erythrocyte sediment rate more than 120 mm/hr, white blood cell count of 18.8 x 109 per liter (L), 82% neutrophils, 12% lymphocytes, 6% monocytes, and hemoglobin of 8.5 g/dL. Computed tomography (CT) scan of the chest showed bilateral ground glass opacities, most prominent in the right lower lobe, consistent with pulmonary edema. There was no evidence of a mass lesion in the chest. Abdominal computed tomography angiography (CTA) showed a retroperitoneal 13.1 x 10 x 5 cm hypodense mass lesion at the L3-L5 level, extending to the bilateral psoas muscles (Figure 1). The mass was associated with bone destruction and sclerosis of the adjacent L4 vertebral body.
Magnetic resonance imaging of the abdomen confirmed a 13.9 x 5.1 x 10.3 cm lobulated retroperitoneal mass extending from the left to right psoas muscle. Possible invasion to the posterior wall of the infrarenal abdominal aorta and ventral L4 vertebral body was seen, raising concern for an infectious or neoplastic process. QuantiFERON-TB testing was negative, as was serologic testing for Treponema pallidum, Cryptococcus, Histoplasma, Coccidioides, and Brucella. Semiquantitative indirect immunofluorescent assay showed high anti-C. burnetii antibody titers: phase I IgG titer of 1 : 16384 with reference range of <1 : 16 (performed by ARUP laboratories) and phase II IgG titer of 1 : 4096 with reference range of <1 : 16 (performed by ARUP laboratories). CT-guided core biopsy was performed to evaluate the retroperitoneal mass, which revealed ischemic necrosis involving skeletal muscle and fibro connective tissue (Figure 2).
Acid-fast bacilli (AFB) and Gomori methenamine silver (GMS) stains were negative for acid-fast bacilli and fungal organisms. Immunohistochemistry for CD34, CD117, S100, and pankeratin was negative. Desmin and myogenin immunostains were positive in benign skeletal muscle.
Because there was a high index of suspicion for a malignant process, a second CT-guided core biopsy was performed one week later; histopathological findings were reminiscent of the first biopsy and showed no evidence of malignancy. At this point, the overall clinical and histopathological findings raised a high index of suspicion for C. burnetii infection. Tissue from the core biopsy was sent to the Health Department of Orange County, California, where a direct PCR test for C. burnetii confirmed the diagnosis. The patient began treatment for Q fever with doxycycline 100 mg twice a day and hydroxychloroquine 600 mg daily. He showed marked clinical improvement with this treatment regime. Three months later, a repeat CT scan showed significant decrease in the size of the retroperitoneal mass, with maximum dimension decrease to 6.5 cm, down from 13.9 cm at presentation. The patient recently completed an 18 month treatment course without complication. Final posttreatment imaging and serology are not available at our institution for review.