title: PET/CT imaging in polymyalgia rheumatica: praepubic18F-FDG uptake correlates with pectineus and adductor longus muscles enthesitis and with tenosynovitis.
abstract: BACKGROUND
  The role of18F-fluorodeoxyglucose positron emission 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, increased18F-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 decrease in praepubic18F-FDG accumulation in response to therapy and to describe potential correlations to other18F-FDG PET/CT scan characteristics during the course of disease. As a secondary objective, we describe the pathological aspects of the observed praepubic18F-FDG uptake.
  
  
  METHODS
  A retrospective review of patients with newly suspected PMR undergoing baseline and follow up18F-FDG PET/CT between February 2010 and March 2016 is given. Those with a visually detected presence of praepubic18F-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 (shoulders, hips, sternoclavicular joints, ischiogluteal bursae, spinous interspaces).
  
  
  RESULTS
  Twenty-three out of 89 screened patients (26%) presented with initial praepubic18F-FDG PET/CT positivity, 15 of whom also underwent follow up18F-FDG PET/CT examination. Five out of 15 patients presented with increased18F-FDG accumulation in large arteries as a sign of giant cell arteritis. During follow up examination, decrease in18F-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 of18F-FDG was diminished in all patients (15/15, 100%) after treatment with steroids.
  
  
  CONCLUSIONS
  Increased praepubic18F-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.
authors.affiliation: Department of Nuclear Medicine and PET Center, Masaryk Memorial Cancer Institute, Brno, Czech Republic; Regional Center for Applied Molecular Oncology (RECAMO), Masaryk Memorial Cancer Institute, Brno, Czech Republic; Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Institute and Faculty of Medicine, Brno, Czech Republic.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Rehak
authors.affiliation: Department of Radiology, University Hospital Brno and Masaryk University, Brno, Czech Republic.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sprlakova-Pukova
authors.affiliation: Institute of Biostatistics and Analyses, Faculty of Medicine, Masaryk University, Brno, Czech Republic.
authors.forename: Zbynek
authors.initials: Z
authors.lastname: Bortlicek
authors.affiliation: Rheumatology Unit, Department of Internal Medicine - Hematology and Oncology, University Hospital Brno and Faculty of Medicine, Masaryk University, Brno, Czech Republic.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Fojtik
authors.affiliation: Department of Radiation Oncology, Masaryk Memorial Cancer Institute and Faculty of Medicine, Masaryk University, Brno, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kazda
authors.affiliation: Department of Anatomy, Faculty of Medicine, Masaryk University, Brno, Czech Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Joukal
authors.affiliation: Department of Nuclear Medicine and PET Center, Masaryk Memorial Cancer Institute, Brno, Czech Republic.
authors.forename: Renata
authors.initials: R
authors.lastname: Koukalova
authors.affiliation: Department of Nuclear Medicine and PET Center, Masaryk Memorial Cancer Institute, Brno, Czech Republic.
authors.forename: Jiri
authors.initials: J
authors.lastname: Vasina
authors.affiliation: Department of Nuclear Medicine and PET Center, Masaryk Memorial Cancer Institute, Brno, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Eremiasova
authors.affiliation: Rheumatology Unit, 2nd Department of Internal Medicine, St. Anne's University Hospital Brno and Masaryk University, Brno, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Nemec
keywords: enthesitis; fluorodeoxyglucose; polymyalgia rheumatica; positron emission tomography; tenosynovitis