Abstract
Diagnosing polymyalgia rheumatica (PMR) is difficult in some cases. We used 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) to observe FDG uptake in the ischial tuberosity, greater femoral trochanter, and spinal spinous process, and when FDG uptake in at least two of these sites is found, the sensitivity and specificity of diagnosing PMR were 85.7% and 88.2%, respectively. Moreover, when compared with the PET findings in late-onset spondyloarthritis (SpA), it was discovered that FDG uptake in the ischial tuberosity, greater femoral trochanter, and spinal spinous process showed no significant difference between SpA and PMR. We thus speculate that the former is reflective of enthesitis at the same site and the latter of bursitis. Meanwhile, FDG uptake in sacroiliac joint inflammation was significantly higher in patients with SpA, which was considered to be a useful diagnostic finding. Furthermore, when compared with the PET findings of elderly onset reumatoid arthritis (EORA)patients, there was a trend for FDG uptake in the ischial tuberosity and spinal spinous process to be higher in patients with PMR than in those with EORA. However, FDG uptake in the wrists was low. In addition, when the FDG uptakes in the shoulders and thighs were carefully observed, EORA patients showed circumferential yet linear FDG uptake surrounding the humeral head reflective of synovitis, whereas PMR patients showed localized yet nonlinear FDG uptake reflective of bursitis. In PMR patients, there was a trend for significant FDG uptake to be observed in the anterior hip joint, indicative of iliopectineal bursitis, which was considered to be very useful for differential diagnosis.
