Background Amyloidosis is a progressive, cumulative process, involving in its early stage only a few structures in some organs, and increasingly more in the later stages of the disease .
Objectives The aim of this study was to study amyloid A deposits in the kidneys of rheumatoid arthritis (RA) patients at death.
Methods A randomized autopsy population of 161 in-patients with RA was studied. AA amyloidosis (AAa) complicated RA in 34 (21.1%) cases. Tissue samples of both kidneys were available for histologic evaluation in 33 of these 34 patients.
The existence of amyloid A deposits in various structures was determined histologically. The extent of amyloid A deposition was evaluated by semi-quantitative, visual estimation on a 0 to 3 plus scale, based on the number of involved blood vessels per light microscopic field (x40 objective of an Olympus BX51).
Results Amyloid deposition is increasing simultaneously in all structures of kidney, but deposition in various structures does not begin at the same time.
Conclusions In manifest amyloidosis the amount of deposited amyloid A protein increases simultaneously in blood vessels and in other renal structures, but deposition does not start at the same time in different structures. Amyloid A deposition starts in the most frequently involved structures of the most frequently involved organ (1).
In the kidneys amyloid A starts depositing in the wall of arterioles and small arteries. Later interstitial collagen fibers, glomeruli, and peripelvic fat tissue are involved. The involvement of peripelvic nerves and cortical basement membranes of the convoluted tubules indicates advanced stages of amyloid deposition in the kidney.
This chronology of amyloid A deposition allows an indirect assessment of the stage of amyloidosis. Based on the involved structures in renal biopsy specimens the pathologist may estimate the involvement of other structures.
Involvement of arterioles alone (without involvement of small arteries) indicates an early stage of amyloidosis, whereas and vica versa amyloid A deposits in peripheral nerves suggests an advanced stage with massive involvement of numerous glomeruli.
Bély M, Apáthy Άgnes: Clinical Pathology of rheumatoid arthritis: Cause of death, lethal complications and associated diseases in rheumatoid arthritis. First English edition. Published by Akadémiai Kiadό, Member of Wolters Kluwer Group. Budapest 2012 http://www.akkrt.hu
Disclosure of Interest None declared