C4A and systemic lupus erythematosus: Among these 43 SLE patients, 12 (27.9%) patients developed active renal flares, 2 (4.6%) developed CNS manifestation, 8 (18.6%) developed active arthritis, 4 (9.3%) developed leukopenia or thrombocytopenia, 22 (51.2%) developed mucocutaneous flares, 23 (53.5%) displayed high anti-dsDNA antibody levels or low C3/C4 complement levels.