DIAGNOSIS OF BETA-2-MICROGLOBULIN ASSOCIATED AMYLOIDOSIS BY SCINTIGRAPHY

This paper discusses recent advances in the non-invasive diagnosis of beta 2-microglobulin amyloidosis (A beta 2M), a widespread complication of long term dialysis therapy. While conventional bone scans or ultrasonography suffer from relative non-specificity, two recent methods, namely scintigraphy with radiolabelled serum amyloid P component (SAP) or with the radiolabelled A beta 2M-precursor protein, beta 2-microglobulin (beta 2M), yield more specific information. Using I-123-labelled SAP, A beta 2M deposits have been visualised in several longterm hemodialysis patients in particular in the wrist area. However, this scan did not show tracer accumulation in other frequently involved sites, such as hips or shoulders, and vice versa frequently labelled the spleen, which is usually spared from A beta 2M deposits. Scanning with I-131-labelled beta 2M, in contrast, yielded tracer accumulations corresponding to the typical distribution pattern of A beta 2M. Specificity of this method was shown by several methods and the sensitivity was found to markedly exceed that of combined clinical and radiological investigations. Recently, both the radiation exposure and the optical resolution of this latter scan have been further refined by substituting I-131 With In-111. Scanning with In-111-beta 2M may therefore provide a basis for future clinical studies on A beta 2M.