IMAGING OF DIALYSIS-RELATED AMYLOID (AB-AMYLOID) DEPOSITS WITH I-131 BETA-2-MICROGLOBULIN

The diagnosis of dialysis-related amyloid (AB-amyloid) has been based usually on clinical and radiological criteria. Following the discovery that beta-2-microglobulin was the major protein of this amyloid, we isolated and radiolabelled uremic plasma beta-2-microglobulin. After intravenous injection, gamma-camera images of selected joint areas were obtained from 42 patients who were on regular hemodialysis therapy. Positive scans involving the shoulder, hip, knee and carpal regions were found in 13 of 14 patients treated for more than 10 years and 10 of 16 patients treated for 5 to 10 years. Patients treated for less time had negative scans. Specificity was indicated by negative scans in non-amyloid inflammatory lesions in control hemodialysis patients. Up to 48-fold tracer enrichment was detected in excised AB-amyloid containing tissue as compared to amyloid-free tissue. These findings suggest that circulating radiolabelled beta-2-microglobulin is taken up by the amyloid deposits. This method may non-invasively detect tissue infiltrates of amyloid. It may also permit prospective evaluation of the efficacy of prophylactic dialysis strategies which are designed to prevent or delay the onset of this complication of long-term dialysis.