Large Vessel GCA Imaging — SCE Rheumatology MCQ

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ModerateMusculoskeletal ImagingLarge Vessel GCA ImagingSCE Rheumatology

A 55-year-old woman with new constitutional symptoms and raised inflammatory markers is diagnosed with giant cell arteritis after specialist assessment. FDG-PET/CT shows smooth, linear mural uptake in the thoracic aorta and bilateral subclavian and axillary arteries, reported as active vasculitis. There is no abnormal temporal artery uptake. Which GCA phenotype is demonstrated?

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Correct answer: B — Extracranial large-vessel GCA

This is extracranial large-vessel GCA: the inflammatory uptake involves the aorta and major proximal branches rather than the temporal arteries. GCA may affect the aorta and its branches with or without demonstrable cranial arterial involvement. EULAR recommends ultrasound, including the axillary arteries, as first-line imaging in suspected GCA; FDG-PET or MRI can alternatively assess cranial and extracranial arteries. PMR alone does not account for vasculitic arterial-wall uptake. Cranial-predominant GCA would require cranial arterial abnormalities. Atherosclerotic uptake is more often focal or patchy and is excluded here by the reported smooth linear vasculitic pattern. Physiological uptake would not be reported as active mural vasculitis. Absent temporal uptake does not absolutely exclude microscopic cranial involvement.

Reference: Dejaco C, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice: 2023 update. Recommendation on imaging in suspected GCA. Ann Rheum Dis. 2024;83:741-751. https://pubmed.ncbi.nlm.nih.gov/37550004/