Diagnosis of Large-Vessel Vasculitis by [18F] Fluorodeoxyglucose–Positron Emission Tomography
A 57-year-old previously healthy woman presented with a history of fever for 6 months, weight loss of 20 kg, and dry cough. Ambulatory antibiotic treatment failed to improve her symptoms. On physical examination (blood pressure, 100/60 mm Hg; heart rate, 64 bpm), she appeared tired, was pale, but was not in acute distress. Lungs and heart appeared normal on auscultation. The abdomen was soft and not tender with normal bowel sounds. The neurological examination was unremarkable. Abnormal laboratory studies included an elevated serum C-reactive protein level (142.1 mg/L; normal <2 mg/L), erythrocyte sedimentation rate (>120 mm the first hour; normal, 7 to 12 mm/h), decreased hemoglobin concentration (5.0 mmol/L; normal, 8.7 to 10.9 mmol/L), and proteinuria (1.7 g/24 h; normal <0.1 g/24 h). Results of other laboratory studies, including leukocyte count with differentials, serum chemistry, liver function test, antinuclear antibody, anti–double-stranded DNA, rheumatoid factor, cryoglobulins, complement, and antineutrophil cytoplasmic antibody, were within normal limits or negative. Serological screening was negative for lues, Borrelia, and hepatitis (A, B, and C). The patient had an acquired immunity to Ebstein-Barr virus and cytomegalovirus with IgG titers. There were no signs for infective endocarditis in transthoracic and transesophageal echocardiography. Bone marrow aspiration and biopsy showed nonspecific changes in hematopiesis in response to an inflammatory process. Chest and sinus x-ray, functional respiratory tests, coloscopy, and abdominal computed tomography scans were normal. A renal biopsy was performed to differentiate the cause of proteinuria. Histologically, a thin basement membrane disease was found, but no evidence of glomerulonephritis was seen.
Because infectious and malignant diseases were excluded and no obvious signs of collagenosis were apparent, the next diagnostic step focused on an inflammatory process of the large vessels. Magnetic resonance imaging (MRI) showed no signs of wall thickening along the entire length of the aorta. Furthermore, in the MR angiography, no intraluminal abnormalities were seen (Figures 1 and 2⇓). Surprisingly, the following 18F-fluorodeoxyglucose (FDG) positron emission tomography revealed extensive FDG uptake in the wall of the thoracic and abdominal aorta and its major branches (Figures 3 and 4⇓). This picture was suggestive of large-vessel vasculitis as seen in Takayasu’s arteritis or Horton’s syndrome. In clinical examination, temporal arteries showed no signs of inflammation. The most conclusive diagnose was Takayasu’s arteritis. An immunosuppressive therapy with prednisone (1 mg · kg−1 · d−1) was started. All symptoms responded to this therapy. Six weeks later, the patient’s C-reactive protein level decreased to 6.5 mg/L and hemoglobin concentration rose to 7.5 mmol/L. A control FDG–positron emission tomography scan at this time showed a significant reduction in FDG uptake with minor residual disease (Figure 4). Steroid treatment was tapered over the next 6 months.
This case illustrates the potential benefit of molecular imaging in the diagnosis of large-vessel vasculitis. Normal MRI or computed tomography scans can be misleading, showing no inflammatory process of vessels. MRI may detect vessel wall edema but was found to be an inconsistent guide to subsequent anatomic changes. In patients presenting with fever of unknown origin or with a marked inflammatory syndrome, the presence of diffuse aortal FDG uptake leads to the rare diagnosis of Takayasu’s arteritis or Horton’s syndrome.1–3
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Andrews J, Mason JC. Takayasu’s arteritis: recent advances in imaging offer promise. Rheumatology (Oxford). 2007; 46: 6–15.