A Histopathological Scoring and Grading System for Renal Non-aa Amyloidosis: Prediction of Clinical Manifestations and Outcomes 

Background: Kidney involvement is a common manifestation that contributes to morbidity and mortality in systemic amyloidosis. Amyloid load can be predicted by histopathological grading of amyloid deposits in kidney biopsy specimens. Our aim was to determine the relationship of renal amyloid deposition grade with clinical manifestations and outcomes in patients with biopsy proven renal non-AA amyloidosis. Methods: : This retrospective cohort study included 74 subjects with renal non-AA amyloidosis (52 AL amyloidosis and 22 unclassified amyloidosis). Baseline characteristics and follow-up data were recorded. Pattern and quantity of amyloid deposition in glomeruli, interstitium, vessels and tubulointerstitial changes were scored. Renal Amyloid Prognostic Score (RAPS) was obtained by addition of all scores and divided into three grades (RAPS grade I, II, III). Results: : In AL amyloidosis group, median follow-up was 11 (4-45 months). Among 52 patients, 17 received autologous stem cell transplantation and 29 received bortezomib based chemotherapy. Baseline eGFR was significantly lower among patients with RAPS grade III. Renal survival was significantly lower among patients with RAPS grade III. Patient survival was not significantly different according to RAPS grade. Type of amyloid could not be determined in 22 patients. In this group, baseline eGFR was significantly lower in patients with RAPS grade III. Conclusions: : In patients with AL amyloidosis, baseline kidney functions are associated with RAPS grade. Renal survival is significantly lower in patients with highest RAPS grade. However, patient survival is not significantly different according to RAPS grade.