AA Amyloidosis of the Liver in Rheumatoid Arthritis - A Postmortem Clinicopathologic Study of 152 Autopsy Patients

The aim of this study was to determine the prevalence and severity of systemic AA amyloidosis (sAAa) in rheumatoid arthritis (RA), to identify the prevalence and amount of amyloid A deposits in different tissue structures of the liver (hAAa), to outline the progression and spead of amyloid A deposition in different tissue structures of the liver, to asses the relationship between sAAa and hAAa, and to determine the role of sAAa and hAAa in mortality.

Patients and Methods: One hundred fiftytwo (152) random autopsy patients with RA were studied. RA was confirmed clinically according to the criteria of the ACR.

The prevalence (existence) and severity (extent) of sAAa and hAAa was specified histologically. Amyloid A deposition was diagnosed histologically according to Romhányi by a modified (more sensitive) Congo red staining.

The extent of amyloid A deposition was evaluated by semi-quantitative, visual estimation on a 0 to 3 plus scale.

Demographics of different patient cohorts were compared with the Student t-probe. The possible relationship between sAAa and hAAa was analyzed with chi-squared (χ2) test.

Results: sAAa complicated RA in 32 (21.05 %) of 152 patients. Branches of blood vessels of different calibers and various tissue structures of the liver were involved in 26 (81.25 % of 32, 17.11 % of 152) cases; hAAa was histologically excluded in 6 (18.75 % of 32) patients with sAAa.

There was a very strong positive relationship between sAAa (n=32) and hAAa (n=26) (c=1.0, χ2=111.9587, p <0.0000).

The hAAa does not appear to be a very serious, life-threatening complication of RA.

Conclusions: sAAa and hAAa may develop in both sexes, and at any time in the course of RA.

sAAa is related to the cardiovascular system, and hAAa is connected with it.

The amyloid A deposition in the liver starts after a latent stage, compared to sAAa of other organs, caused by not specified local protective mechanism.

sAAa and hAAa is a progressive and cumulative process, involving in its early stage only a few structures, and increasingly more in later stages of the disease.
The chronology of amyloid A deposition allows an indirect assessment of the stage of sAAa or hAAa, which may have a prognostic value in biopsies.

Amyloid A deposition on the liver cell plates may be an appropriate cleaning mechanism as well, but the role of the reticuloendothelial system (Kupffer cells, sinus endothelial, and perisinusoidal Ito cells) in blood clearance also cannot be ruled out.

Keywords: Rheumatoid arthritis, systemic AA amyloidosis, AA amyloidosis of the liver.