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Paget disease (PD) is a chronic disorder resulting in enlarged and misshapen bones, caused by disorganized bone remodeling. This case involves a 64-year-old man with prostatic adenocarcinoma and PD of some skeletal areas with increased uptake shown on 18 F-fluoro-methyl-choline (FMC) positron emission tomography/ computed tomography (PET/CT) performed for cancer restaging. Besides this feature, Paget disease may mimic metastases on PET/CT using various radiotracers, including 18 F-FMC PET/CT. In particular, this case highlights the potential of multiparametric disease characterization on PET. Therefore, in suspected cases, in which differential diagnosis is difficult, histology can be a helpful tool for diagnostic purposes.

During the past decades autoimmune diseases have been usually treated with immunosuppressive drugs mostly active on T-Cell mediated responses. Only in recent years, with our extended knowledge of the pathogenic mechanisms of autoreactive disorders and the tremendous development of new therapeutic monoclonal antibodies, anti-B-Cell therapies have emerged as a new option for treating autoimmune diseases. The rationale for this changeover from T-Cell to B-Cell targeted therapies resides in the recently accumulated evidence of the role of B-Cells in the pathogenesis of autoimmune diseases and in the generation of tissue damage. Targeting memory and effector BCells may then disrupt the production of pathogenic antibodies, counteract the role of B-Cells in sustaining antigen presentation to T-Cells and block the synthesis of B-Cell activation cytokines. The anti-CD20 monoclonal antibody Rituximab was first introduced more than 20 years ago for the treatment of CD20+ chronic B-lymphoproliferative disorders, and was then successfully experimented in the treatment of an ever-increasing spectrum of autoimmune diseases. Newer anti-CD20 monoclonal antibodies have been introduced more recently, which vary in their biological effects. The need for laboratory indicators that may help the rational usage and follow-up of anti-CD20 treatments has now emerged, due to the high variability of individual response, to the markedly different outcomes in the various diseases and to the controversial role of pathogenic autoantibodies as indicators of disease activity. Flow cytometric (FCM) analyses to identify and enumerate the B-cell functional subsets in the peripheral blood have been developed in recent years. They can be used to assess the degree and the persistence of memory B-Cell depletion, the quality and the timing of B-Cell reconstitution, along with the highly sensitive FCM counting technique needed for the detection of extremely low cell levels. The long-term aim of this innovative approach is to provide clinicians with a tool for a safer and more rational usage of anti-CD20 agents.

18F-fluorodeoxyglucose positron emission tomography/computed tomography (18-FDG-PET/CT) is a functional imaging technique which is an established tool in oncology, and has also demonstrated a role in the field of inflammatory diseases, such as large vessel vasculitis (LVV). In the last few years, it is known that atherosclerotic lesions with inflammation, detected by FDG-PET, are high-risk structural features and more likely to lead to subsequent progression of atherosclerosis with more clinical complications.

Immune checkpoint inhibitors (ICIs) targeting cytotoxic T-lymphocyte associated protein-4 (CTLA-4), programmed cell death protein-1 (PD-1), and its ligand PD-L1 are established cancer immunotherapies for solid tumor and hematologic malignancies. These therapies are involved in immune-related adverse events (irAE), both general and rheumatic ones. In general, immune-related adverse events (irAE) management includes drug-holding, tapering doses of corticosteroids, and specific immunosuppression for clinically severe cases, such as infliximab or mycophenolate.