Renal amyloidosis. Correlations between morphology, chemical types of amyloid protein and clinical features

Sixty-one autopsy cases of renal amyloidosis were reviewed to assess the relationship of renal pathology to chemical types of amyloid and clinical features. Glomerular amyloid deposition was divided on the basis of morphological characteristics, into four types: a mesangial nodular type showing nodular mesangial deposits with sparse capillary wall involvement (25 cases), a mesangio-capillary type disclosing diffuse amyloid deposition in the mesangium and along both sides of the glomerular basement membrane (19 cases), a perimembranous type principally involving the subepithelial side of the basement membrane invariably characterized by exuberant spicular arrangement (6 cases), and a hilar type showing amyloid deposits almost exclusively in hilar arterioles (11 cases). Twenty-four of 25 cases of mesangial nodular type (96%) showed amyloid protein of AA type. However, mesangio-capillary and perimembranous types were associated with deposition of AL amyloid protein in 15 of 19 (79%) and all 6 cases, respectively. Nephrotic syndrome was more frequent in patients with AL amyloidosis; notably, all patients with perimembranous type had nephrotic syndrome irrespective of the extent of glomerular amyloid deposits. Chronic renal failure and renal death appeared more common in mesangial nodular type in which the extent of glomerular amyloidosis correlated with that of vascular amyloid deposits. The results obtained suggest that the chemical type of glomerular amyloid protein (AA vs AL) is associated with significant differences in the morphological, clinical and prognostic features of the renal involvement.