How is dialysis-related beta-2-microglobulin (beta-2m) amyloidosis diagnosed?

Updated: Nov 14, 2019
  • Author: Anita Basu, MD, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

The diagnosis of beta-2m amyloidosis is established primarily by its clinical appearance on tissue or bone biopsy.

Obtaining a biopsy of the affected bone or synovium, followed by routine hematoxylin and eosin staining, reveals homogeneous eosinophilic material. Amyloid deposits are positive for Congo red staining, showing green birefringence of the amyloid fibrils under polarized light. Specific immunostaining of amyloid deposits by monoclonal anti ̶ beta-2m antibody confirms the diagnosis of beta-2m amyloidosis.

Antisera to amyloid beta-2m are taken up by the Congo red–positive areas, but are not taken up in other types of amyloidosis. On electron microscopy, typically, 8-10 nm wide, nonbranching, curvilinear fibrils are observed in beta-2m amyloidosis.

The reference range of the serum concentration of beta-2m is 1.5-3 mg/L, while in amyloidosis, serum levels can be elevated to values of 50-100 mg/L. However, an increase in beta-2m levels does not confirm the diagnosis of beta-2 amyloidosis, as these levels are usually elevated with low glomerular filtration rates. Hematologic studies frequently reveal a normochromic, normocytic anemia.


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