Characterising polymyalgia rheumatica on whole-body 18F-FDG PET/CT: an atlas

The impact of modern imaging in uncovering the underlying pathology of PMR cannot be understated. Long dismissed as an inflammatory syndrome with links to the large vessel vasculitis giant cell arteritis (GCA), a pathognomonic pattern of musculotendinous inflammation is now attributed to PMR and may be used to confirm its diagnosis. Among the available modalities, F-18-fluorodeoxyglucose (F-18-FDG) PET/CT is increasingly recognized for its high sensitivity and specificity, as well as added ability to detect concomitant large vessel GCA and exclude other relevant differentials like infection and malignancy. This atlas provides a contemporary depiction of PMR's pathology and outlines how this knowledge translates into a pattern of findings on whole body F-18-FDG PET/CT that can reliably confirm its diagnosis. Lay Summary PMR is the most common inflammatory rheumatic disease of older people. It typically causes disabling pain and stiffness in affected individuals at the shoulders and hips. Until recently, the precise cause for these symptoms was poorly understood. Modern scans using whole-body PET/CT (an advanced imaging test that shows where inflammation is in the body) and MRI have now identified characteristic muscle and tendon inflammation around the shoulder and hip joints, in addition to other features within the spine and at the knees and wrists/hands. This unique appearance has resulted in increasing use of PET/CT to aid PMR diagnosis in everyday clinical practice and research settings. These major advances in our knowledge are highlighted in this atlas, alongside typical examples of PMR's appearance on whole-body PET/CT.