Childhood-onset Lupus Nephritis Initial Glucocorticoid-dose Harmonization Trial (LIGHT Trial)

Inclusion Criteria: * Age ≥6 years and \<18 years, with body weight ≥20 kg * Meets the 2019 European League Against Rheumatism (EULAR) and American College of Rheumatology (ACR) classification criteria for Systemic Lupus Erythematosus (SLE) * Renal biopsy confirming Lupus Nephritis class III, IV, III+V, or IV+V according to the International Society of Nephrology / Renal Pathology Society (ISN/RPS) classification * At screening: 24-hour urinary protein ≥1.0 g (or ≥25 mg/kg), or urine protein-to-creatinine ratio (UPCR) ≥1.0 g/g * White blood cell count ≥3.0 × 10⁹/L and lymphocyte count ≥1.0 × 10⁹/L * No prior intravenous methylprednisolone pulse therapy before enrollment, and glucocorticoid exposure ≤2 weeks before enrollment, with a maximum prednisone-equivalent dose ≤30 mg/day (or ≤1 mg/kg/day) * Written informed consent obtained and good treatment compliance expected Exclusion Criteria: * Uncertain diagnosis of SLE, genetically confirmed monogenic lupus, or a history of immunodeficiency * Severe infection, including hepatitis C, active hepatitis B, HIV infection, tuberculosis infection, severe fungal infection, etc. * Severe neuropsychiatric lupus * Peripheral blood hemoglobin \<60 g/L, platelet count \<10 × 10⁹/L, or concomitant aplastic anemia * Severe cardiac insufficiency (NYHA functional class ≥ II) * Severe pulmonary involvement, including pulmonary hemorrhage, respiratory failure, pulmonary embolism, or other conditions requiring respiratory support * Estimated glomerular filtration rate (eGFR) \<60 mL/min/1.73 m² * Severe gastrointestinal bleeding, pancreatitis, or hepatic lesions * Patients deemed by the investigator to be unsuitable for participation in this trial