Urinary Congophilia as an Indicator of Activity of Lupus Nephritis

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease that can affect all body organs. The reported lifetime incidence of lupus nephritis (LN) in SLE patients is 20%- 60% and it is histologically evident in most SLE patients, even without clinical manifestations of kidney disease .

Lupus nephritis is associated with higher mortality , as within 5 years of diagnosis, between 10 and 30 percent of these people develop end-stage renal disease . Early detection and treatment of lupus nephritis can significantly improve renal outcomes and decrease overall mortality .

Endoplasmic reticulum (ER) stress proteins, which act as protein quality control factors in the secretory pathway in the cell are induced by ER stress in inflammatory lesions, and also participate in autoimmunity and inflammation processes, ER stress proteins are expressed not only in the ER but also occasionally at the cell surface that plays pathophysiological roles in autoimmune and inflammatory diseases as pro- or anti-inflammatory factors, Protein folding is easily impaired (misfolding) by different cytotoxic stresses as inflammation or hypoxia , that may contribute to disease pathogenesis by either reducing the biological activity of the protein or due to toxicity by the misfolded proteins, The detection of the abnormally misfolded proteins using the Congo red stain is referred to as congophilia, Urinary congophilia was assessed by Congo Red Dot Blot (CRDB) Assay Congo red is a synthetic diazo dye with specific affinity for β-sheets of amyloid fibrils of misfolded proteins, In addition to the simplicity of congophilia based dot blot technique, the non-invasiveness of the method is useful in adapting the CRDB assay for self-collected urine samples.

One previous study in pregnant females with lupus nephritis said that urinary congophilia has a diagnostic value in patients with lupus nephritis and can be used as a reliable marker of disease activity as the presence of urinary congophilia biomarker is related to disease activity rather than pregnancy.

Inclusion criteria

• Adult patients ≥ 18 years old that were diagnosed with SLE according to EULAR/ACR classification criteria 2019 for SLE, and lupus nephritis based on renal biopsy or active urinary sediment (proteinuria or hematuria )

Exclusion criteria

• Any patient has evidence of nephritis that may cause proteinuria as diabetes mellitus and any other causes of glomerulonephritis other than lupus nephritis
• pregnant females with lupus nephritis and hypertensive disorders