Circulating microparticles bearing Fibrin associated with whole-body 18FDG-PET: diagnostic tools to detect paraneoplastic polymyalgia rheumatica.

Polymyalgia rheumatica (PMR), a chronic inflammatory rheumatism, can be the expression of a paraneoplastic syndrome. The same clinical symptoms are frequently observed at the early stage of the benign and malignant forms. Here, our aim was to develop diagnostic tools to differentiate paraneoplastic PMR from essential PMR. We combined an 18FDG-PET and detection of circulating procoagulant microparticles (MPs), such as fibrin positive (FibMPs), by flow cytometry. Two patients with PMR and a similar profile were selected. In the two patients, the 18FDG-PET revealed a hypermetabolic focus. However, the concentrations of fibrin+/annexin+ microparticles detected were (10 times higher in one of the two patients, who was later found to have breast cancer. The association of 18FDG-PET and the detection of microparticle fibrin positives by flow cytometry allows separating essential PMR (hypermetabolism by 18FDG-PET, low FibMPs) from paraneoplastic PMR.