Description Patient, 60 years old. In 2018, symmetrical non-erosive arthritis of the hand joints appeared. According to tests: ACCP, RF, ESR, CRP – normal, ANA – negative. Seronegative rheumatoid arthritis (DAS28 4.7) was diagnosed and methotrexate (MT) 22.5 mg/week was prescribed with a positive effect. Due to arthritis recurrence two years later, methylprednisolone (MP) 4 mg/day, hydroxychloroquine (HCQ) 200 mg/day and MP IV total 1250 mg were prescribed. Then MT dose was increased to 25 mg/week, HCQ to 400 mg/day. In January 2022, the patient had mild COVID-19 confirmed by RT-PCR. On 23/01/22, she was treated with a combination of monoclonal antibodies against SARS-CoV2 surface S-protein (Bamlanivimab 700 mg + Etesivimab 1400 mg). In March 2022, examination revealed arthritis, urtic rash. There were laboratory abnormalities: CRP 6.2mg/L(0–5), ANA 1/320cytopl, anti-dsDNA 200IU/ml(0–25), anti-C1q 24.4IU/ml(0–10), C3 0.83g/L(0.9–1.4). Echocardiography showed no pathology. Given the chronological relationship with the administration of monoclonal antibodies, the late age of onset and the absence of visceral organ involvement, drug-induced lupus (DIL) with skin involvement (anti-C1q vasculitis) was initially diagnosed. Therapy: MP IV 1500 mg total, oral MP 8 mg/day, HCQ 400 mg/day, MT 20 mg/week with positive effect – reduction of arthritis and rash elements. However, considering the persistence of immunological abnormalities (anti-dsDNA 800IU/ml, anti-C1q 27.9IU/ml, C3 0.756g/L) by November 2022, the diagnosis is revised in favor of systemic lupus erythematosus (SLE), SELENA-SLEDAI 4 without clinical manifestations.

Conclusions There are known cases of the development of DIL/SLE against the background of therapy with monoclonal antibodies, mainly TNF-α inhibitors. However, SLE after therapy with Bamlanivimab and Etesivimab are not described in the literature. Dynamic monitoring of the patient allowed to establish a final diagnosis and to prescribe an adequate and effective therapy.