FRI0026 SYSTEMIC, RENAL AND CARDIAC AA AMYLOIDOSIS IN RHEUMATOID ARTHRITIS – A COMPARATIVE POSTMORTEM CLINICOPATHOLOGIC STUDY OF 161 PATIENTS

Objectives: The aim of our study was to determine the incidence of systemic AA amyloidosis (sAAa) in RA, to appraise the prevalence and severity of amyloid A deposits in different tissue structures of the kidneys and heart, to outline the development of renal and cardiac AA amyloidosis (rAAa and cAAa), and to estimate the role of rAAa and cAAa in mortality. Methods: One hundred sixty one (161) non- selected autopsy patients with rheumatoid arthritis (RA) were studied. RA was confirmed clinically according to the criteria of the ACR [1]. sAAa was specified histologically, based on evaluation of 5 organs (heart, lung, liver, kidney and pancreas). Amyloid A deposition was diagnosed histologically according to Romhanyi by a modified (more sensitive) Congo red staining [2]. Amyloid A deposits were confirmed in serial sections by immunohistochemical and histochemical methods. Results: sAAa complicated RA in 34 (21.12%) of 161 patients; in 127 (78.88%) of 161 patients amyloid A deposits were not found. Amyloid A deposits were found in 29 (87.88%) kidneys of 33 patients with sAAa; kidneys were negative for amyloid in 4 (12.12%) of 33 cases (in 1 of 34 patients with sAAa tissue blocks of kidneys were not available). Amyloid A deposits were found in 29 (87.88%) hearts of 33 with sAAa; the heart was negative for amyloid in 4 (12.12%) of 33 cases (the heart of one patient with sAAa was not available). Renal amyloid A deposition led to death in 17 (50.0% of 34) patients with sAAa due to massive amyloid A deposition in the kidneys, leading to renal insufficiency and uremia. Cardiac amyloid A deposition led to death in 3 (8.82% of 34) patients with sAAa (and contributed to the lethal outcome in further 5). Forteen (41.18% of 34) patients with sAAa died of other causes such as peritonitis, lethal septic infection, etc. sAAa was clinically diagnosed in 9 (26.47%) and missed in 25 (73.52%) of 34 patients, and only cases with massive renal amyloid A deposits were recognized. Cardiac AAa or its pathogenic role in mortality was not diagnosed. Conclusion: sAAa is one of the main and the most insidious complications of RA affecting the kidneys and heart with high prevalence and severity. sAAa is related to the cardiovascular system, and rAAa or cAAa are associated with it. sAAa, rAAa and cAAa may developed in both sexes, and at any time in the course of the disease. Systemic, renal and cardiac amyloid A deposition is a progressive and cumulative process, involving in its early stage only a few structures in some organs, and increasingly more in the later stages of the disease. In sAAa the renal and cardiac amyloid A deposition starts after a latent stage. This latency may be caused by a not specified local protective mechanism, e.g. great excretion capacity of the kidneys, due to motility of the heart or oxygenisation etc. Amyloid A deposition starts in the most frequently involved structures of the kidneys or heart with more massive deposits. The chronology of amyloid A deposition allows an indirect assessment of the stage of renal or cardiac amyloidosis, which may have a prognostic value in everyday surgical pathology. Half of the patients with sAAa died of uremia caused by massive rAAa and only 9 of these were clinically recognized. Renal and cardiac amyloid A deposition should be considered a very serious, life-threatening complication of RA. References: [1] Arnett FC, et al: Arthritis Rheum, 1988; 31: 315-324. DOI: 10.1002/art.1780310302 [2] Bely M, Makovitzky J: Acta Histochemica 108, 175-180 (2006). DOI: 10.1016/j.acthis.2006.03.017 Disclosure of Interests: None declared