Background Amyloidosis is a progressive, cumulative process involving in its early stage only a few tissue structures in some organs, and increasingly more in later stages of the disease (1).
Objectives The aim of this study was to characterize the development of AA amyloidosis (AAa) in RA patients with mild or massive amyloid deposits at death.
Methods A randomized autopsy population of 161 in-patients with RA was studied. AAa complicated RA in 34 (21.1%) patients; with minimal or moderate amyloid A deposits (<1) in 21 (61.8%), and massive amyloid A deposits (1£) in 13 (38.2%) cases (2).
RA was confirmed clinically according to the criteria of ACR.
Amyloid A deposits in different tissue structures of 17 organs (gastrointestinal tract, heart, kidney, spleen, adrenal gland, liver, pancreas, lung, thyroid gland, aorta, skeletal muscle, synovial membrane, lymph node, peripheral nerve, bone (head of femur), skin and brain) were determined histologically and their extent was evaluated by semi-quantitative, visual estimation on a 0 to 3 plus scale.
Results As demonstrated in Figure l, in patients with mild or severe amyloidosis the amount of amyloid A deposits at death (arranged according to the increasing values of amyloid A deposits/patients) was nearly linear and ran parallel.
Mild or severe amyloidosis progressed at the same rate; only the amount of amyloid A deposits was different (Figure 1).
Conclusions The precursors of amyloid A protein fibrils are produced by the liver. Serum amyloid A proteins spread via the bloodstream and deposit throughout the body. The level of precursors in the blood depends on the production and/or elimination of amyloid proteins or, more succinctly, on the dynamics of these two processes.
We found no difference in the linear and basically parallel development of amyloidosis between patient groups with moderate and massive amyloid A deposition. The progression of amyloid deposition was the same in both patient groups suggesting differences in production of precursors.
The extent and quantity of amyloid deposits in various organs at death depend on the volume of the organs and on the volume of blood per minute reaching them. The ratio of organ-mass and the volume of blood per minute do not change basically (under normal circumstances), therefore the rates of amyloid deposits in different organs (the differences of amyloid A deposits between various organs) are constant and do not change during the course of amyloidosis. This allows a new approach to the histological diagnosis of systemic AA amyloidosis and facilitates an indirect assessment of amyloid deposits in various organs (3).
Quantitative differences in production of serum amyloid A may be related to a “benign” or “aggressive” clinical course of RA, which may be due to genetical and other factors.
Bély M, Apáthy Ά, Pintér T, Ratkό I: Generalized secondary amyloidosis in rheumatoid arthritis. Acta Morph. Acad Sci Hung 1992;40:49-69.
Bély M, Apáthy Ά: Clinical pathology of rheumatoid arthritis: Cause of death, lethal complications and associated diseases in rheumatoid arthritis. First English edition, 1-440 pp. Akadémiai Kiadό, Budapest 2012 http://www.akkrt.hu
Bély M, Apáthy Ά: Indirect assessment of amyloid A deposits in various organs. Ann Rheum Dis 2014;73(Suppl 2): DOI: 10.1136/annrheumdis-2014-eular.1229
Disclosure of Interest None declared