Clinical Utility of Serum Ribonuclease 1(RNASE1) as a Biomarker of Lupus Nephritis.

Systemic lupus erythematosus (SLE) is a chronic, multisystem autoimmune disease that has a heterogeneous clinical presentation, ultimately leading to damage of multiple organs. Lupus nephritis (LN) constitutes one of the most severe organ manifestations of SLE. Understanding of the genetic and pathogenetic basis of LN has improved substantially over the past few decades. However, despite this increased knowledge and improved treatment options LN remains a substantial cause of morbidity and death among patients with SLE .

Renal biopsy remains the gold standard for diagnosing LN and evaluating histological activity and prognostication . However, its invasive nature limits repeated assessment and longitudinal monitoring. In practice, serological markers such as (C3and C4), (dsDNA) antibodies, and routine laboratory parameters including proteinuria and serum creatinine are commonly used to evaluate disease activity . These markers have limited sensitivity and specificity, and their fluctuations often fail to fully reflect parallel histological changes in the kidney. Therefore, the identification of reliable and non-invasive biomarkers that better capture both systemic immune activation and renal involvement remain an important unmet need.

Ribonuclease 1 (RNASE1) is a secreted endoribonuclease predominantly produced by endothelial cells and plays an essential role in the degradation of extracellular RNA . These are suggested to promote endothelial activation, immune cell infiltration and activation, so promote inflammatory responses . Since that endothelial dysfunction & inflammatory signalling are central mechanism in LN pathogenesis, dysregulation of RNASE1 mediated extracellular RNA clearance may contribute to renal inflammatory injury, suggesting RNASE1 as a potential biomarker in LN .

Inclusion criteria

• Adult patients (≥18 years old) with non lupus nephritis SLE diagnosed according to the 2019 EULAR/ACR Classification Criteria for Systemic Lupus Erythematosus .
• Adult patients (≥18 years old) with Lupus Nephritis classified according to the 2018 ISN/RPS classification criteria.

Exclusion criteria

• Patients less than 18 years old
• Patients with other autoimmune diseases
• Active infection and malignancy
• Pregnancy and lactation
• Inability to provide informed consent