Per-protocol Repeat Kidney Biopsy in Incident Cases of Lupus Nephritis

Inclusion Criteria: * Fulfilment of the EULAR/ACR classification criteria of SLE. * 18 years of age or above. * Incident biopsy-proven proliferative or membranous LN, or combinations thereof (with UPCR ≥ 1 g/g), i.e. 2003 ISN/RPS class III (A or A/C) ± V, class IV (A or A/C) ± V, or class V. * Consent to the possibility of a repeat kidney biopsy at month 12 from baseline. * Initiation of the following treatment regimens: * intravenous pulses of methylprednisolone (total dose of 500-3000 mg); * oral prednisone or equivalent 0.3-0.5 mg/kg/day with tapering; * hydroxychloroquine unless contraindicated; * angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs); * either one of mycophenolate mofetil (MMF) equivalent dose 2-3 g/day, or IV cyclophosphamide (CYC) according to the Euro-Lupus regimen; * the NIH protocol for IV CYC (0.5-0.75 g/m2 monthly for six months) could be considered in severe cases; * add-on therapies (e.g. calcineurin inhibitors, biologics) to the above two regimens are optional. Exclusion Criteria: * Antiphospholipid syndrome nephropathy (APSN). * Pregnancy at baseline (pregnancy during follow-up will not lead to exclusion). * Medical contraindications to kidney biopsy, e.g. thrombocytopenia \< 50,000/μL, uncontrolled hypertension or end-stage kidney disease (ESKD). * Anticipated non-adherence to therapy. * Medical conditions interfering with outcome evaluations. * Inability to read and/or sign the informed consent form.