IMAGING AND SEROLOGICAL PROFILING OF PATIENTS WITH POLYMYALGIA RHEUMATICA AND GIANT CELL ARTERITIS

Background: Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are two inflammatory conditions affecting people aged over 50 years. PMR is characterized by pain and stiffness in the shoulder and hip girdles. GCA, a large vessel vasculitis, is the most common form of primary systemic vasculitis. About 40-60% of patients with GCA present with concomitant PMR, and histologic features consistent with GCA can be detected on temporal artery biopsy of about 16% to 21% of patients with PMR. It is still debated whether PMR and GCA are different conditions or represent different clinical manifestations across the spectrum of a single disease. The aim of this research project was to profile immunological and imaging aspects of these two conditions to better characterize their similarities and differences. Patients and methods: A cohort of unselected, consecutive patients with PMR, GCA or both was studied. PMR was diagnosed according to Bird et al. criteria, whereas patients with cranial (C)-GCA were diagnosed according to the 1990 ACR classification criteria; a subset of these patients underwent temporal artery biopsy. Five further patients with fever of unknown origin (FUO) and imaging evidence of large vessel vasculitis (LVV) were included. All patients underwent a detailed and standardized clinical examination and, subsequently, a 18F- Fluorodeoxyglucose (FDG) positron emission tomography (PET) scan.. Joint and vascular uptake were evaluated by a qualitative visual score, using the liver uptake as a reference, and with semi-quantitative mean standardized uptake value (SUV). Each value of the qualitative joint and vascular scores of every region were summed up to obtain a total joint score (TJS) and a total vascular score (TVS). In a subgroup of patients, serum samples were collected just before the injection of FDG on the same day of the PET scan. The soluble (s) immune checkpoints cytotoxic T-lymphocyte antigen-4 (CTLA-4), soluble programmed death-1 (sPD-1) and programmed death-ligand 1 and 2 (PD-L1 and PD-L2) were measured in this subgroup. The serum of fifty healthy controls were studied for comparison. Results: One hundred and thirty-one patients underwent FDG-PET/CT scanning, including 89 females and 42 males, with a median age of 74 years (range 47-92). Ninety-seven patients were diagnosed as PMR, 13 as C-GCA, 16 with both PMR and C-GCA and five patients presented with FUO. Soluble CTLA-4, sPD1, sPD-L1, and sPD-L2, evaluated in 40 patients (32 with PMR and 8 with PMR+C-GCA), were increased in comparison with controls (p<0.001 for all the comparisons), although no statistically significant difference between patients with PMR+C-GCA and those with isolated PMR was found. Conclusions: Patients with PMR and GCA share many immunological and imaging abnormalities. Results from this study demonstrate that available and evaluated biomarkers are unable to precisely differentiate these two conditions.