SAT0152 Systemic and renal aa amyloidosis in rheumatoid arthritis – a comparative postmortem clinicopathologic study of 161 patients

Objectives: The aim of our study was to determine the prevalence and severity of systemic AA amyloidosis (sAAa), to specify amyloid A deposits in different tissue structures of the kidneys, to outline the development of renal AA amyloidosis (rAAa), and to estimate the role of sAAa and rAAa in mortality. Methods: At the National Institute of Rheumatology 9475 patients died between 1969 and 1992; among them 161 with RA (females 116, average age: 64.95 years, range 87–16, onset of RA: 50.19, average disease duration: 14.79 years; males 45, average age: 66.29 years, range 88–19, onset of RA: 52.57, average disease duration: 13.46 years at death); who were autopsied. RA was confirmed clinically according to the criteria of the ACF. sAAa was specified histologically, based on evaluation of 5 organs (heart, lung, liver, kidney and pancreas) in each of 161 patients. Amyloid A deposition was diagnosed histologically according to Romhanyi by a modified (more sensitive) Congo red staining. Amyloid A deposits were identified in serial sections by immunohistochemical and histochemical methods. The prevalence (existence) and severity (extent) of amyloid A deposition were evaluated microscopically with an Olympus BX51 polarizing microscope. 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). sAAa was lethal in 17 (50.0 % of 34) patients 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. Conclusions: sAAa is one of the main and the most insidious complications of RA affecting the kidneys with high prevalence and severity. sAAa is related to the cardiovascular system, and rAAa is associated with it. sAAa and rAAa may developed in both sexes, and at any time in the course of the disease. Systemic and renal amyloid A deposition is a progressive and cumulative process, involving in its early stage only a few structures in various organs, and increasingly more in the later stages of the disease. In sAAa the renal 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. Amyloid A deposition starts in the most frequently involved structures of the kidneys with more massive deposits. The chronology of amyloid A deposition allows an indirect assessment of the stage of renal 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 amyloid A deposition should be considered a very serious, life-threatening complication of RA. Disclosure of Interest: None declared