PET/CT imaging in polymyalgia rheumatica: Praepubic 18F-FDG uptake correlates with pectineus and adductor longus muscles enthesitis and with tenosynovitis
The role of 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG PET/CT) is increasing in the diagnosis of polymyalgia rheumatica (PMR), one of the most common inflammatory rheumatic diseases. In addition to other locations, increased 18F-FDG accumulation has been detected in the praepubic region in some patients. However, a deeper description and pathophysiological explanation of this increased praepubic accumulation has been lacking. The aim of the presented study is to confirm a decline in praepubic 18F-FDG accumulation in response to therapy and to describe potential correlations to other PET/CT scan characteristics during the course of disease. As a secondary objective, we describe the pathological aspects of the observed praepubic 18F-FDG uptake.
Material and Methods
A retrospective review of patients with newly suspected PMR undergoing baseline and control PET/CT between February 2010 and March 2016 is given. Those with a visually detected presence of praepubic 18F-FDG accumulation were further analysed. The uptake was assessed visually and also semi-quantitatively in the defined region of interest by calculation of target-to-liver ratios. Other regions typical for PMR were systematically described as well. MRI targeted for description of praepubic location was performed in one patient with extraordinary uptake.
Twenty-three out of 89 screened patients (26%) presented with initial praepubic 18F-FDG PET/CT positivity, 15 of whom also underwent control PET/CT examination. Five patients (33%) presented with increased 18F-FDG accumulation in large arteries as a sign of giant cell arteritis. During control examination, decrease in 18F-FDG accumulation caused by therapeutic intervention was observed in all evaluated locations in all analysed patients and no new positivity was indicated, including periarticular, extraarticular tissues or target large vessels. Praepubical accumulation of 18F-FDG was diminished in all patients (15/15, 100%) after treatment with steroids. MRI finding suggested tenosynovitis, pectineus muscle and adductors enthesitis and was not correlated to eventual bursitis.
Increased praepubic 18F-FDG uptake in patients with PMR is relatively common and this region should be systematically evaluated during differential diagnosis of rheumatic and malignant disease. Praepubic inflammation is probably related to enthesitis and tenosynovitis at the origin of pectineus and adductor longus muscles ventrally from the pubis.