Coronavirus disease 2019 (COVID-19) is associated with autoimmunity and systemic inflammation. Patients with autoimmune rheumatic and musculoskeletal disease (RMD) may be at high risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In this review, based on evidence from the literature, as well as international scientific recommendations, we review the relationships between COVID-19, autoimmunity and patients with autoimmune RMDs, as well as the basics of a multisystemic inflammatory syndrome associated with COVID-19. We discuss the repurposing of pharmaceutics used to treat RMDs, the principles for the treatment of patients with autoimmune RMDs during the pandemic and the main aspects of vaccination against SARS-CoV-2 in autoimmune RMD patients.

The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) pathways are known to play a key role in B-cell activation and fibrosis in systemic sclerosis (SSc). Receptors of B-cell activator factor (BAFF) utilize these pathways, which can be influenced by Toll-like receptors (TLRs), as TLRs can alter the expression of BAFF-binding receptors. Our results show that B-cell stimulation via TLR homologue CD180 phosphorylates Akt in diffuse cutaneous SSc (dcSSc) to a lower extent than in healthy controls (HCs). We found basal downregulated BAFF receptor (BAFF-R) and enhanced transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) expression in dcSSc B cells, which might enhance the formation of autoantibody-secreting plasma cells. Moreover, this pathological shift was observed in naive B cells, emphasizing the importance of their increase in SSc. Additionally, we measured higher serum levels of autoantibodies to BAFF in dcSSc patients, suggesting that an imbalance in the complex system of BAFF/anti-BAFF autoantibodies/BAFF-binding receptors may contribute to the development of SSc. Anti-CD180 antibody treatment had opposite effects on the expression of BAFF-R and TACI in HC B cells, resulting in similar levels as observed in SSc B cells without stimulation, which argues against the usefulness of such therapy in SSc.