Coronavirus disease 2019 (COVID-19) can manifest with a wide range of extrapulmonary symptoms and have longterm consequences (so-called post-covid syndrome (PCS) or “long COVID-19”). Manifestations of PCS show a wide clinical spectrum and include cardiac, pulmonary, neurological, gastrointestinal, dermatological, mental symptoms, vascular thrombosis and avascular necrosis (AVN) of the bones.We present our own observations of the development of bone’s AVN in 3 patients who underwent COVID-19 with bilateral lung disease, in whom after 4–6 months the first signs of AVN were noted and characterized by a progressive multifocal lesion, which was accompanied by an increase of C-reactive protein concentration.The pathogenetic mechanisms of AVN development in the framework of PCS are discussed. The importance of conservative and surgical methods in the treatment of the disease are considered. Since the development of AVN of various localizations with a long latent period is possible after COVID-19, long-term monitoring of patients is required. Further study of the problem of PCS in general and AVN in particular is required.

The problem of prevention of coronavirus disease 2019 (COVID-19) in patients with immune-mediated inflammatory rheumatic diseases (IMRD) remains highly relevant. The presence of IRD is associated with a high risk of disease and severe course of COVID-19 during immunosuppressive treatment, primarily anti-B cell therapy with rituximab (RTX), and a low level of post-vaccination response in such patients. A new strategy for the prevention and treatment of COVID-19 are virus-neutralizing monoclonal antibodies to coronavirus; currently, combined long-acting monoclonal antibodies tixagevimab and cilgavimab (Evusheld) are registered for prevention in the world and the Russian Federation. . Tixagevimab and cilgavimab (TC) show neutralizing activity against SARS-CoV-2, including the Omicron strain, primarily its variants BA.4, BA.5, BA.2.75 ("Centaur").Objective – to evaluate the efficacy and safety of TC for pre-exposure prophylaxis of COVID-19 in rheumatic patients receiving RTX, based on a prospective observational study.Materials and methods. The main group included 86 patients with various IMRD receiving RTX: 50 of them had ANCA-associated systemic vasculitis (AAV), 15 – rheumatoid arthritis, 9 – Sjogren’s syndrome (SS), 4 – IgG4-related disease, 3 – systemic lupus erythematosus (SLE), 3 – dermatomyositis (DM), 2 – systemic scleroderma (SSD). Median age was 59 (19–82) years; male : female ratio – 1:1,8. From March 26 to August 30 2022, patients received a single intramuscular injection of TC in a total dose of 300 mg, mainly after RTX (in 52% of cases, in 28% on the next day after RTX). The control group included 42 patients with AAV (median age – 45 (35–71) years; male : female ratio – 1:1), also treated with RTX, who did not receive pre-exposure prophylaxis of TC. The duration of observation was 7 months, until November 1 2022. At this time, 98% of confirmed cases of coronavirus in the Russian Federation were Omicron. A telephone and/or online survey of patient has been conducted to detect cases of COVID-19 and adverse reactions.Results. In the TC group, confirmed coronavirus infection have been detected in 17 (20%) patients (AAV – 10, SS – 3, SSD – 2, SLE – 1, DM – 1), with fever in 7 (8%), only in one case hospitalization was required (lung damage was not detected in computed tomography), in two cases, according to CT mild lung damage (CT 1–2), there were no deaths. Good TC’s tolerability was noted, signs not associated with COVID-19 or progression of IMRD after administration of TC were observed in 8 (9%) patients (GPA – 3 MPA – 1, RA – 2, SLE – 1, IgG4-related disease – 1), adverse reactions definitely associated with the use of TC were not found. The most serious event not associated with coronavirus infection was the progression of polyneuropathy in a patient with RA. In the control group, 3 (7%) patients were diagnosed with COVID-19, one with severe lung injury (CT 3, pulmonary embolism) and death.Conclusions. The data of clinical studies and our own clinical experience evidence the effectiveness of the use of a combination of long-acting monoclonal antibodies TC (Evusheld), registered for indications for pre-exposure prophylaxis and treatment of COVID-19. Patients with IMRD treated with RTX have a favorable safety profile of TC. The introduction of virus-neutralizing monoclonal antibodies, a new drug class for the prevention and treatment of infectious diseases, opens significant prospects for improving the prognosis of patients with IRD.