Clinical Correlation of Histopathological Classification, Scoring, and Grading in Amyloid Nephropathies: Single-Center Experience

Abstract

Objective: Amyloidosis is disorder of various etiologies in which abnormally folded fibrillary protein deposits with more than thirty forms infiltrate into extracellular spaces of affected organs. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The aim of present study was to classify and grade renal amyloidosis cases using renal amyloid prognostic score (RAPS) systems, correlate clinical data and chronic kidney disease (CKD) stages. Methods: We retrospectively analyzed kidney biopsies of 45 patients diagnosed with renal amyloidosis applied between 2017-2022 to our department and scored each of patients according to RAPS. Results: 8.9% of patients had RAPS score 1, 53.3% had 2 and 37.8% had 3. Urea, serum creatinine and proteinuria levels of RAPS3 patients were significantly higher and eGFR levels were lower compared to RAPS1 patients (p<0.01). According to CKD stages, no significant difference was observed in glomerular amyloid deposition class and score, vascular and interstitial amyloid deposition scores, and glomerular sclerosis (p>0.05). The interstitial fibrosis, inflammation values and RAPS scores were found to be significantly higher in advanced CKD stages (p<0.05). Majority of patients at CKD stage 1-2 had RAPS score 2 (73.68%), while 57.1% of at stage 3 and 66.7% at stage 4-5 had RAPS score of 3 (p=0.0015). Conclusion: As a result, the intestinal fibrosis, inflammation values, RAPS scores were significantly higher in advanced CKD stages. Distribution pattern of amyloid in the renal parenchyma compartment, grade of RAPS and eGFR were associated with urea/creatinine, proteinuria levels and thus with CKD stage.