Background All types of amyloid deposits may be present in rheumatoid arthritis (RA) as an associated phenomenon, or as a complication of associated diseases, but only AA amyloidosis (AAa) may be considered as a true complication of RA.
Cerebral amyloid angiopathy (CAA) is characterized by deposition of amyloid beta (Ab) peptides in the wall of leptomeningeal and cerebral arteries and arterioles (localized to the brain only). CAA may be present in up to 90% of Alzheimer’s disease (AD), and 40% of CAA with dementia show changes of AD at autopsy (1).
Objectives The aim of this study was to determine the prevalence and histological characteristics of CAA (with or without AD) in patients with RA.
Methods A randomized (non-selected) autopsy population of 161 in-patients with RA was studied. Samples of brain tissue (frontal, parietal and temporal lobe, pons, medulla oblongata, cerebellum) covered by leptomeninges were examined. CAA was histologically diagnosed.
Results Ab deposits were observed in 2 (1.24%) of 161 patients (a 75-year old female and a 74-year old male patient, duration of RA 15 and 30 years, resp.), without clinical evidence of AD, or manifest dementia.
The Ab deposits were focally localized to the walls of small arteries and arterioles of the leptomeninges. In the parietal and temporal lobe of the brain Ab deposits were seen in the wall of arterioles. No amyloid deposits were detected in the wall of venules and veins of the leptomeninges or the brain. Extravascular Ab deposits in so-called amyloid plaques of the brain were not present. The Ab deposits were accompanied in both patients by multiple small cerebral infarcts and cerebral edema (without acute or chronic cerebral hemorrhage).
The direct cause of death of both patients was independent of CAA: the female patient died of multifocal brain infarction due to cerebral manifestation of systemic vasculitis and the man died of sepsis as a complication of purulent arthritis of the left knee joint and of both shoulder joints.
Conclusions CAA in our two patients may be considered as an independent accompanying phenomenon of RA without the classical clinical symptoms of AD.
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 (2). Amyloid deposition begins in organs and tissue structures that are frequently involved and later show marked deposition of amyloid. On the other hand, where deposits are infrequent or less marked, amyloid deposition starts later (2).
In case of CAA the Ab protein deposition begins in the wall of small arteries and arterioles of leptomeninges. Arterioles of the cortical and subcortical region of brain tissue will be involved later. This chronologic sequence is supported by the observed decreased prevalence and amount of Ab deposits in smaller vessels of leptomeninges and arterioles of the brain. Blood returning from the brain does not contain significant amounts of Ab protein and therefore the veins are spared of Ab deposits. Extracerebral systemic Ab deposition is not to be expected in CAA which is, evidently, an isolated pathological process, localized to the brain.
The Ab deposits in blood vessels may be accompanied by edema and microinfarcts of the brain possibly producing symptoms.
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Bély M, Apáthy Ά, Pintér T, Ratkό I. Acta Morph Acad Sci Hung, 1992; 40:49-69
Disclosure of Interest None Declared