Diffuse large vessel giant cell arteritis Dx with PET scan:
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An 85-year-old woman was referred for investigation of unexplained nausea, anorexia, malaise, and weight loss of 7 kg over 3 months. She had a history of mild Alzheimer's dementia. Physical examination was unremarkable—specifically, there were no noteworthy abdominal signs. Repeated measurements of her erythrocyte sedimentation rate (ESR) revealed moderately raised values ranging from 47 mm/h to 53 mm/h.

Full blood count showed she was anaemic with haemoglobin concentrations ranging from 9·5 g/dL to 7·9 g/dL. She also had a neutrophil leucocytosis with values varying between 12·1 × 109 per μL and 17·9 × 109 per μL. The patient's serum C-reactive protein (CRP) varied from 139 mg/L to 170 mg/L. She had low-grade pyrexia 3 days after admission, with her temperature ranging from 37·3°C to 37·9°C.

However, no source of sepsis was found after clinical examination. Baseline investigations for exploration of pyrexia or inflammation of unknown origin were undertaken; a chest x-ray, urine and blood cultures, echocardiography, microbial serology, and autoantibody screening were all negative. CT scans of her thorax, abdomen, and pelvis were undertaken to rule out the possibility of an occult tumour or an abscess; they were normal.

Values of her ESR and CRP remained elevated and blood cultures were repeatedly negative. The 18Fluorodeoxyglucose PET/CT was planned and the images revealed a marked increase in tracer uptake in the thoracic and abdominal aorta, and the subclavian, carotid, and axillary arteries—consistent with widespread vasculitis. A biopsy of the temporal artery was done, and subsequent histological examination showed a classic picture of giant cell arteritis (GCA).

The patient was commenced on oral prednisolone at a daily dose of 1 mg/kg. Within 4 days, her constitutional symptoms had resolved, and she was able to eat regular meals without nausea. Values of her CRP and ESR reverted to normal, and the low-grade pyrexia resolved fully.

Major takeaway:-
- This case illustrates that GCA can sometimes present with non-specific and atypical features-particularly in patients later in life.

- Additionally, 18Fluorodeoxyglucose PET/CT imaging can be highly useful for finding the cause of pyrexia or inflammation that has not been identified using the usual methods of investigation.

Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)30117-5/fulltext