Imaging techniques in the diagnosis of dialysis-related amyloidosis

beta (2)-microglobulin amyloidosis (A beta M-2) is a major determinant of m orbidity in patients on dialysis treatment. Symptoms of A beta M-2 amyloid are mainly related to (peri-)articular amyloid deposition. Imaging techniqu es [i.e., joint ultrasonography, X-ray, computed tomography (CT), or magnet ic resonance imaging (MRI) findings], as well as conventional bone scans, a re helpful in the screening of local lesions but are relatively nonspecific and/or not sensitive enough. Scintigraphic techniques using radiolabeled s erum amyloid P component (SAP) or the radiolabeled A beta M-2 precursor pro tein, beta M-2, generate more specific results. A beta M-2 deposits have be en visualized in several long-term hemodialysis patients by using I-123-lab eled SAP. However, this scan did not show tracer accumulation in some frequ ently involved sites such as hips or shoulders, and frequently labeled the spleen, which is usually spared from A beta M-2 deposits. Improvements in t echnical sensitivity and specificity could be achieved by scanning with I-1 31-labeled beta M-2: this technique detected tracer accumulations correspon ding to the typical distribution pattern of A beta M-2. Further, both the r adiation exposure and the optical resolution of this latter scan have been refined by substituting In-111 for I-131. In a final step we generated reco mbinant human beta M-2 (rh beta M-2). While In-111 rh beta M-2 again failed to show significant tracer accumulation over joint regions in patients on short-term hemodialysis without evidence of A beta M-2, local tracer accumu lations similar to those observed with natural, In-111-labeled beta M-2 cou ld be demonstrated in long-term hemodialysis patients with evidence of A be ta M-2. In conclusion, scintigraphy for A beta M-2 with In-111-labeled rh b eta M-2 provides a homogeneous and safe recombinant protein source and repr esents a suitable detection method of beta M-2 amyloid deposits in dialysis patients.