We conducted a prospective study to investigate whether a correlation exists between the clinical course of renal involvement and the pathological findings of renal amyloidosis in patients with rheumatoid arthritis (RA).
Patients with RA of more than 5 years' duration and who did not show renal manifestations were selected and received a duodenal biopsy for the diagnosis of amyloidosis. After the diagnosis of AA amyloidosis, patients received a renal biopsy, and patterns of amyloid deposition were examined. We followed the renal functions (serum levels of blood urea nitrogen and creatinine) of patients diagnosed with AA amyloidosis for 5 years.
We diagnosed 53 patients with AA amyloidosis and monitored the renal function of 38 of them for > 5 years. The histological patterns were examined; in the 38 patients there were appreciable variations in the patterns of amyloid deposition. In 27 patients, amyloid deposits were found exclusively in the glomerulus (type 1). In the other 11 patients, however, amyloid deposits were found selectively around blood vessels and were totally absent in the glomerulus (type 2). In type 1 patients with glomerular involvement, renal function deteriorated rapidly regardless of disease state; most patients received hemodialysis. In type 2 patients with purely vascular involvement, however, renal function did not deteriorate significantly.
In patients with RA and AA amyloidosis, 2 distinct clinical courses in terms of renal involvement were identified. It is suggested that renal function does not deteriorate when amyloid deposition is totally lacking in the glomerulus.