Abnormal high expression of fibroblast activating protein (FAP) has been found in inflammatory reactions and benign fibrosis tissue. Autoimmune nephropathy such as lupus nephritis (LN) can lead to tubular atrophy and excessive deposition of extracellular matrix, which may be accompanied by abnormally increased expression of activated FAP in kidney tissue, and lead to renal fibrosis and long-term renal failure. This makes 68Ga-labeled FAP inhibitor (FAPI) positron emission tomography (PET) imaging the potential to early assess disease severity, predict disease progress and aid treatment planning in patients with LN. Compared to renal pathological puncture, 68Ga-FAPI PET is a new tool for non-invasive, repeatable assessment of renal fibrotic activation.

Inclusion Criteria:

• Be between 18-80 years old;
• Confirmed SLE: meet the 2019 EULAR/ACR classification standards;
• There are signs of renal involvement and indications for renal puncture: proteinuria> 0.5g/24 hours (or urine protein creatine ratio (UPCR) >500mg/g), unexplained decrease of glomerular filtration rate (GFR)

Exclusion Criteria:

• The pathology of renal puncture is not consistent with lupus nephritis;
• Previous history of other kidney diseases;
• There are contraindications to renal puncture: (1) obvious bleeding tendency, (2) severe hypertension, (3) psychosis or non-cooperative patients, (4) isolated kidney, (5) small kidney;
• History of malignant tumors within 5 years.