C3 and systemic lupus erythematosus: The diagnosis of SLE was made according to the European League Against Rheumatism and the American College of Rheumatology 2019 (EULAR/ACR2019) diagnostic criteria [7] with a score of 19 (fever, leukopenia, alopecia, rash, pleural or pericardial effusion, and low C3 and C4) (Table 1).