C3 and systemic lupus erythematosus: The new-onset clinical features and positivity of SLE-specific antibodies constitute a score of 24 on the 2019 EULAR/ACR classification criteria (fever = two points, thrombocytopenia = four points, joint involvement = six points, antiphospholipid antibodies = two points, low C3 and C4 = four points, SLE-specific antibodies = six points), establishing a diagnosis of SLE [5].