Uda H et al. (2006) Two distinct clinical courses of renal involvement in rheumatoid patients with AA amyloidosis. J Rheumatol 33: 1482–1487

A number of patients with chronic inflammatory conditions, such as rheumatoid arthritis (RA), develop amyloid A (AA) amyloidosis, a condition characterized by the extracelluar deposition of serum AA protein-containing fibrils. Renal involvement is frequent. Many patients develop end-stage renal disease by the time AA amyloidosis is confirmed, resulting in a poor prognosis. Researchers working in Japan have, however, identified a group of patients with RA who retained normal renal function for more than 5 years following diagnosis of AA amyloidosis.

In a prospective study, Uda et al. examined the relationship between renal function and amyloid deposition in the kidneys of 38 patients with AA amyloidosis. All patients had received a diagnosis of RA more than 5 years previously and had normal renal function at the time that AA amyloidosis was diagnosed. From renal biopsy results, the researchers identified two distinct amyloid deposition patterns: deposition in glomeruli, with or without deposits around blood vessels (type 1, 27 patients); and deposition solely around blood vessels (i.e. no deposition in glomeruli; type 2, 11 patients). During 5 years of follow-up, the renal function of patients with type 1 amyloid deposition deteriorated rapidly, and most commenced hemodialysis. By contrast, patients with type 2 amyloid deposition did not exhibit a marked deterioration in renal function during follow-up and none began dialysis. Patients with type 1 amyloid deposition had a 5-year survival rate of only 41.2% from the point of AA amyloidosis diagnosis, compared with 90.9% for patients with type 2 deposition.