Imaging techniques in the diagnosis of dialysis-related amyloidosis

beta(2)-microglobulin amyloidosis (A beta(2)M) is a major determinant of morbidity in patients on dialysis treatment. Symptoms of A beta(2)M amyloid are mainly related to (peri-)articular amyloid deposition. Imaging techniques [i.e., joint ultrasonography, X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) findings], as well as conventional bone scans, are helpful in the screening of local lesions but are relatively nonspecific and/or not sensitive enough. Scintigraphic techniques using radiolabeled serum amyloid P component (SAP) or the radiolabeled A beta(2)M precursor protein, beta(2)M, generate more specific results. A beta(2)M deposits have been visualized in several long-term hemodialysis patients by using (123)I-labeled SAP. However, this scan did not show tracer accumulation in some frequently involved sites such as hips or shoulders, and frequently labeled the spleen, which is usually spared from A beta(2)M deposits. Improvements in technical sensitivity and specificity could be achieved by scanning with (131)I-labeled beta(2)M: this technique detected tracer accumulations corresponding to the typical distribution pattern of A beta(2)M. Further, both the radiation exposure and the optical resolution of this latter scan have been refined by substituting (111)In for (131)I. In a final step we generated recombinant human beta(2)M (rh beta(2)M). While (111)In rh beta(2)M again failed to show significant tracer accumulation over joint regions in patients on short-term hemodialysis without evidence of A beta(2)M, local tracer accumulations similar to those observed with natural, (111)In-labeled beta(2)M could be demonstrated in long-term hemodialysis patients with evidence of A beta(2)M. In conclusion, scintigraphy for A beta(2)M with (111)In-labeled rh beta(2)M provides a homogeneous and safe recombinant protein source and represents a suitable detection method of beta(2)M amyloid deposits in dialysis patients.