Classification of Renal Amyloidosis Based on Histologic Glomerular Involvement

Amyloid Deposition in the Glomerulus	Class
none	0
minimal	I
minimal, mesangial	II
mesangiocapillary, focal	III
mesangiocapillary, diffuse	IV
membranous	V
advanced	VI

 

Minimal amyloid deposition

glomeruli involved: <= 50%

amyloid deposits within an affected glomerulus: < 10%

amyloid deposits seen on H&E: no

amyloid deposits: focal and segmental within vascular pole and/or mesangium

 

Minimal mesangial amyloid deposition

glomeruli involved: <= 50%

amyloid deposits within an affected glomerulus: 10-25%

amyloid deposits seen on H&E: yes

amyloid deposits: focal and segmental within vascular pole and/or mesangium

 

Focal mesangiocapillary amyloid deposition

glomeruli involved: <= 50%

amyloid deposits within an affected glomerulus: 26-50%

amyloid deposits seen on H&E: yes

amyloid deposits: focal and segmental within vascular pole and mesangium.

may have deposits in vessels and the medullary interstitium.

may have minimal tubulointerstitial deposits

should not have diffuse glomerular involvement

 

Diffuse mesangiocapillary amyloid deposition

EITHER

glomeruli involved <= 50% and amyloid deposition 51-75%

OR

glomeruli involved > 50% and amyloid deposits <= 75%

amyloid deposits seen on H&E: yes

may have significant tubulointerstitial deposits

may have diffuse glomerular deposits within capillaries and/or global glomerular sclerosis

 

Membranous amyloid deposition

glomerular amyloid deposition: diffuse membranous pattern

mesangial deposits: none or minimal (not prominent)

amyloid deposits seen on H&E: yes

 

Advanced amyloid deposition

glomeruli involved: > 50%

amyloid deposits within an affected glomerulus: >= 76%

amyloid deposits seen on H&E: yes

may have glomerular amyloid balls

may have global glomerular sclerosis

interstitial inflammation and fibrosis with prominent tubular loss

 

Conditions that should be classified as Class I:

(1) minimal focal membranous deposition

(2) hereditary amyloidosis without glomerular involvement

(3) renal allograft with tubulointerstitial and/or vascular involvement without glomerular deposits

(4) familial Mediterranean fever (FMF) patient treated with colchicine