Polymyalgia rheumatica and interspinous FDG uptake on PET/CT.

Polymyalgia rheumatica (PMR) is an inflammatory disease with macrophage infiltration and CD4+ T-lymphocytes-related mild synovitis commonly causing neck, shoulder, and hip stiffness in patients older than 50 years. Closely related to giant cell arthritis (GCA), PMR symptoms can be similar to rheumatoid arthritis. Erythrocyte sedimentation rate and C-reactive protein levels are elevated in >90% of cases. In 4 patients with PMR, (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrates uptake in the shoulder and hip joints and also interspinous and supraspinous focal and diffuse uptake. We propose diffuse uptake may reflect ligament inflammation with focal uptake in adjacent interspinous bursitis.