Beta2-microglobulin and amyloidosis.

Dialysis-associated amyloidosis is a serious complication in chronic dialysis patients. Its clinical expression in terms of arthralgias, destructive arthopathies and carpal tunnel syndrome is often associated with amyloid deposits, which are mainly composed of beta2-microglobulin (beta2-M) fibrils, but in addition contain a number of other compounds. It is probable that beta2-M-amyloid deposition is related, at least in part, to the elevated plasma beta2-M that is characteristic of chronic renal failure. The latter can decrease with high-performance dialysis techniques but cannot be reduced to the normal range. Almost certainly, several other systemic and local factors are involved, including beta2-M transformed by advanced glycation end products and advanced oxidation protein products, serum P component, ubiquitin, calcium crystals, cytokines, immunoglobulin light chains, proteases and antiproteases, as well as modified collagen and glucosaminoglycans. It is also possible that the beta2-M protein, in its native or modified form, exerts noxious effects on bone and joint tissues, in addition to its mere 'passive' presence as amyloid fibrils. Several retrospective studies and one prospective study suggest that dialysis strategies with highly permeable, synthetic membranes and/or ultrapure dialysate may be partially protective or at least delay the onset of dialysis amyloidosis. Successful kidney transplantation generally halts the disease process and leads to rapid relief of osteoarticular pain although regression of beta2-M-amyloid deposits probably does not occur.