Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease of unknown etiology characterized by hyperproduction of autoantibodies. The problems of timely diagnosis and identification of predictors of an unfavorable outcome of SLE are relevant due to the variable clinical picture and a high risk of 5-year mortality in the absence of treatment. The purposes of this research were to assess the frequency of various variants of SLE onset, to identify trigger factors contributing to the development of the disease and to analyze the degree of disease activity in children. Materials and methods used: a single-center cohort retrospective study was conducted involving patients aged 9 to 17 y/o who had undergone inpatient treatment at the rheumatological department of the Morozov Children’s City Clinical Hospital (Moscow, Russia) in 2020-2023, specifying age, gender, assessing the frequency of observed symptoms of SLE onset, disease activity according to the SLEDAI scale, laboratory parameters and drug treatment. Results: total of 45 records were analyzed: 75.5% (34) girls/24.5% (11) boys; median age 15 [13; 15] y/o; most frequent clinical syndrome was cutaneous (75.5%); kidney damage was noted in 40% of cases. 86.6% had hematological disorders as follows: thrombocytopenia and leukopenia (48.9%), anemia (46.6%): Coombs-positive anemia (71.4%), lymphopenia (37.7%) and increased ESR (66.6%). Antinuclear factor (ANF Hep2) was detected in all cases. According to the SLEDAI-2K scale, the median disease activity was 11 [7; 16] points. Low disease activity (less than 6 points) was observed in 4.4% (2), average (6 to 10 points) in 44.4% (20), high (11 to 19 points) in 37.7% (17), above average (over 20 points) in 13.3% (6). Moreover, disease activity was higher in girls (p=0.940) and a relationship was found between the time required for diagnosis and disease activity according to the SLEDAI-2K scale (p=0.206). Drug therapy: glucocorticoids (GCS) orally in all cases, intravenous pulse GCS therapy in 71.0%. Hydroxychloroquine therapy was prescribed in 100.0%, mycophenolate mofetil in 57.7%, intravenous immunoglobulin in 37.7%, cyclophosphamide in 13.3%, methotrexate in 6.6%, biological therapy in 31.0%, the drug of choice was rituximab. Conclusion: updating the data on the frequency of various variants of SLE debut as well as identifying the new trigger factors contributing to the development of the disease are necessary steps aiming to increasing the awareness of the SLE course with its debut in childhood, optimizing the diagnosis process and reducing the risk for complications.