Beta-2 Microglobulin Amyloidosis

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The two major forms of amyloidosis are AL amyloidosis (in which light chains form the amyloid deposits) and AA amyloidosis (in which a variety of inflammatory molecules may adopt a beta-pleated structure to deposit as amyloid.

A specific subset of AA amyloidosis which is secondary to dialysis is beta-2 microglobulin amyloidosis. Beta-2 microglobulin (B2M) is an 11.8 kD protein which is a subunit of the MHC Class I molecule and is normally filtered and catabolized by the kidney. In the absence of renal function, large serum concentrations of B2M may build up and deposit, specifically synovial membranes, tendones, and bone. This leads to a stereotypic syndrome of carpal tunnel syndrome, flexor tenosynovitis, and other musculoskeletal manifestations which may be quite debilitating.

The GOOD NEWS is that this disease is not seen nearly as much as previously. It is hypothesized that the use of high flux dialyzers–which have a larger pore size than previously favored dialyzers and therefore would allow for the clearance of middle molecules such as as B2M–has made B2M amyloidosis a thing of the past.

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