Clinicopathological study of renal amyloidosis and its relationship with renal amyloid prognostic score

Introduction: The kidney is one of the most common organs involved in systemic amyloidosis. Several studies have attempted scoring kidney amyloid deposits and predicting the outcome. A new scoring and grading scheme is proposed, known as renal amyloid prognostic score (RAPS), which provides a better means for scoring renal amyloidosis and predicting renal outcome. Objectives: The present study aims to estimate the clinicopathological and biochemical parameters in renal amyloidosis cases and the role of RAPS in assessing renal outcome and prognosis. Materials and Methods: This retrospective study included all diagnosed cases of renal amyloidosis from October 2017 to December 2021. Detailed clinical features and laboratory parameters were obtained from medical records, and all renal biopsies were studied using light microscopy (LM) and immunofluorescence. Congo red-stained sections were examined under a polarizer to look for amyloid deposits. RAPS was calculated on a scale of 0 to 31 and was graded from 0 to III. Pearson’s correlation coefficient was calculated between RAPS and serum creatinine, as well as between RAPS and estimated glomerular filtration rate (eGFR). Results: Fourteen cases of renal amyloidosis were included, comprising seven cases of primary amyloidosis, of which six showed lambda light chain restriction. RAPS varied from 12 to 27. There was a strong correlation between RAPS and serum creatinine (r= 0.7) and a moderate negative correlation between RAPS and eGFR (r=-0.5). Conclusion: Application of RAPS and, thus, uniform reporting of renal amyloidosis helps assess the disease’s severity.