[Morphogenesis of beta 2m (A beta 2m) amyloid deposits in dialysis patients]

beta 2m related amyloidosis (A beta 2m) is a late complication of renal replacement therapy (RRT), first identified in 1980. It is preferentially located in the joints. Its clinical manifestations and risk factors have been clearly delineated. Still, its true prevalence and the factors determining the fibrillar precipitation of beta 2m remain to be defined. A prospective autopsy study of the joints of dialyzed patients, confirms that A beta 2m prevalence increases with dialysis duration and age of the patients at the onset of RRT. Prevalence is not significantly different according to the modality of RRT, hemo--or peritoneal dialysis. Of great interest is the finding that histologic evidence of A beta 2m preceeds by over five years the onset of clinical symptoms. The detailed study of A beta 2m deposits has allowed their classification into 3 successives stages: stage 1, impregnation of the cartilage; stage 2, extension to capsules and synovia; stage 3, invasion of synovial and capsular deposits by macrophages. In the first 2 stages, in the absence of macrophages, there is no immunohistochemical evidence of advanced glycation of the A beta 2m. We conclude that neither macrophages nor the advanced glycation of beta 2m are prerequisities of A beta 2m formation.