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Takayasu’s arteritis (TA) is an uncommon chronic vasculitis of unknown origin that affects large and medium sized arteries, especially the aorta, its branches and pulmonary arteries.1,2 TA may present as fever of unknown origin (FUO),3 and inflammatory cells have been shown to take up [18F]fluorodeoxyglucose ([18F]FDG) avidly.4–6
A 27 year old woman was admitted for FUO, headache, and interscapular pain, radiating to the neck and shoulders in the past 2 months. Physical and vascular examinations were normal. Laboratory tests showed anaemia (haemoglobin 84 g/l) and a raised erythrocyte sedimentation rate (ESR 79 mm/1st h). Blood cultures, a Venereal Disease Research Laboratory (VDRL) test, and autoimmune serological findings were negative. Vascular magnetic resonance (VMR) was normal. [18F]FDG positron emission tomography ([18F]FDG-PET) showed hypermetabolism in the brachiocephalic trunk, left carotid artery, and thoracic aorta (fig 1A).
Treatment was started with methylprednisolone (1 mg/kg/day; 60 mg) and methotrexate (15 mg/week). The pain disappeared quickly after starting treatment. At 7 months of follow up the patient remained asymptomatic. Laboratory tests improved (haemoglobin 110 g/l; ESR 8 mm/1st h). [18F]FDG metabolism was normal (fig 1B). When the methylprednisolone dose was reduced below 16 mg/day, the pain reappeared in the left cervical zone, upper chest, and back. The ESR was higher (16 mm/1st h) and [18F]FDG-PET showed hypermetabolism again, matching the painful zones (fig 1C).
A 21 year old woman presented with FUO within the past year and neck pain radiating to the left shoulder within the past month. Physical examination showed a thrill in the right supraclavicular fossa, but no bruits were detected. Upper limbs pulses were normal. Laboratory tests showed anaemia (haemoglobin 80 g/l) and a raised ESR (72 mm/1st h). Blood cultures, VDRL test, and autoimmune serological findings were negative. VMR was normal. [18F]FDG-PET showed hypermetabolism in the thoracic aorta, carotids, brachiocephalic trunk, and pulmonary trunk (fig 2A).
Treatment was started with methylprednisolone (1 mg/kg/day; 60 mg) and methotrexate (15 mg/week), with fast clinical and biochemical response. At 4 months of follow up she remained asymptomatic, but radial pulse and blood pressure were undetectable in the left arm. Doppler ultrasonography showed brachial artery thrombosis with collateral neovasculature. Laboratory tests showed haemoglobin 110 g/l and ESR 11 mm/1st h. The dose of methylprednisolone was maintained at 30 mg/day. No other symptoms appeared until 3 months later, when methylprednisolone was reduced to 20 mg/day. She presented with upper thoracic pain and weakness in both arms. Haemoglobin was 111 g/l but ESR was 77 mm/1st h. [18F]FDG-PET showed significant inflammatory activity (fig 2B).
[18F]FDG-PET has been shown to be a useful diagnostic tool in FUO7 and in some types of vasculitis,4,5 including TA.6,8 It allows an early diagnosis of TA8 during the inflammatory or “pre-pulseless” phase,1,2 when other techniques such as VMR or arteriography may be normal. This point is crucial because the “pre-pulseless” phase will not fulfil the American College of Rheumatology criteria for TA, which are mostly based on advanced disease.1 An early diagnosis allows early treatment and, theoretically, it might reduce the risk of complications.
Moreover, [18F]FDG-PET can identify more vascular regions affected by the inflammatory process than VMR5 and quantify the inflammatory activity of the disease.6 This is important, because 44% of patients in clinical remission have histologically proven inflammatory activity1,2 and blood inflammatory markers are still limited.9 In addition, [18F]FDG-PET is useful in assessing the effectiveness of different treatments during follow up6 and could be used in randomised controlled trials. However, [18F]FDG-PET should be compared with more standardised techniques, such as angiography, VMR, computed tomography, or Doppler ultrasound to obtain firm support for its value in clinical practice.
The accuracy of [18F]FDG-PET for diagnosing TA has been estimated as 94% and false positives are not found in normal patients aged under 40.6 In our patients PET was the only technique with a positive result for diagnosing TA and showed good correlation with disease activity. Our experience also confirms previous reports of relapsing TA after tapering the corticoid dose,2,9 even though methotrexate was started after diagnosis.
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