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 deposition in the heart of rheumatoid arthritis (RA) patients at the time of 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 heart were available for histologic evaluation in 33 of these 34 patients. RA was confirmed clinically according to the criteria of ACR. The presence of amyloid A deposits in various structures of the heart was determined histologically. The extent of amyloid A deposition was evaluated by semi-quantitative, visual estimation on a 0 to 3 plus scale.
Results Detectable amounts of amyloid A deposits in different tissue structures of the heart did not appear at the same time.
In the early stage of systemic amyloidosis there were histologically detectable amyloid deposits only in a few structures (arterioles, interstitial collagen fibers, small arteries). In other structures of the heart (venules, small veins, myocardiocytes, medium size veins and arteries, nerves) deposits were seen only in late stages of amyloidosis (with massive involvement of the previously mentioned structures).
The amount of deposited amyloid A was different in various tissue structures and increased simultaneously, but the proportion of deposited amyloid A was constant and independent of the stage of amyloidosis. The sequence and progressive cumulative character of amyloid A deposition in various structures of the heart are demonstrated in Figure 1.
Conclusions Simultaneously in different tissue structures (the number of involved structures and the amount of deposited amyloid A increases with progression of the disease). The amount of deposited amyloid A protein increases simultaneously in blood vessels and in other structures of the heart, but deposition does not start at the same time in various structures. Amyloid A deposition starts in the most frequently involved structures of the most frequently involved organ .
In the heart amyloid A deposition starts in the wall of arterioles and interstitial collagen fibers. Later small arteries, reticulin fibers (collagen IV) of epicardial fat tissue, venules and small veins are involved. The involvement of myocardiocytes, medium size veins and arteries, furthermore nerves indicate advanced stages of amyloid deposition in the heart.
This chronology of amyloid A deposition allows an indirect assessment of the stage of amyloidosis. Based on the involved structures in heart biopsy specimens the pathologist may estimate involvement of the other structures.
Involvement of arterioles alone (without involvement of small arteries) indicates an early stage of amyloidosis, whereas and vice versa amyloid A deposits in peripheral nerves or myocardiocytes suggests an advanced stage with massive involvement of other cardiac structures.
Bély M, Apáthy Άgnes, Pintér T, Ratkό I. Generalized secondary amyloidosis in rheumatoid arthritis. Acta Morph. Acad Sci Hung 1992;40:49-69
Bély M, Apáthy Άgnes. Clinical pathology of rheumatoid arthritis: Cause of death, lethal complications and associated diseases in rheumatoid arthritis. 1-440 pp. Akadémiai Kiadό, Budapest 2012 http://www.akkrt.hu
Disclosure of Interest None declared