A 82-year-old man with a medical history of Dyslipidemia, Hypertension, and glaucoma, presented with a 3-week history of fever of unknown origin and a rash. Physical examination was notable for erythematous papular rash over his trunk, fatigue and weight loss was recorded. Laboratory studies showed hemoglobin levels of 7.6 g/dL (reference range 14–17 g/dL) and thrombocytosis of 600·103/µL (reference range 150–450 103/µL). Ferritin levels of 1300 ng/milliliter (reference range 22–277 ng/ml) and ESR level of 120 mm/h (reference range < 20 mm/h). Serological tests for infectious agents as well as rheumatoid panels were all non-diagnostic. To support the diagnosis of FUO; PET/CT was done; the patient was prepared according to known recommendations (Slart et al. 2018). PET/CT showed involvement of cranial and extra-cranial vessels including superficial temporal, maxillary, vertebral and occipital arteries, as well as medium size vessels such as subclavian, brachial, femoral, and tibial arteries (Fig. 1). Despite the high physiologic FDG uptake in the brain, we noted that temporal artery and bilateral upper and lower extremity arteries had higher uptake than the surrounding tissue, a grade 2, and higher uptake than the liver’s, meaning grade III. SUVmax was 4.1 left temporal artery, 4.3 in axillary and brachial arteries, and 7.5 in femoral, popliteal and tibial arteries. Thoracic aorta was not significantly involved, SUVmax 3.5 (Nielsen et al. 2019; Stellingwerff et al. 2015; Slart et al. 2018; Nienhuis et al. 2020); Thus, a GCA diagnosis was presumed. Despite the abscess of jaw claudication and headaches, an ultrasound was done due to confirm the diagnosis however US and cytological findings of the temporal arteries were non-remarkable of the presumption of skips lesions. Based on the widespread distribution and typical pattern on PET/CT, a diagnosis of giant cell arteritis was made. Glucocorticoid treatment was started, followed by a rapid and marked improvement of symptoms and inflammatory markers.
