Soft-tissue uptake of 99mTc-diphosphonate in systemic AL amyloidosis

A case of systemic AL (amyloid light-chain-derived) amyloidosis is presented, in which a 99mTc-diphosphonate bone scan demonstrated the intense uptake of tracer in the liver, spleen, heart, thyroid, oropharyngeal region, intestinal tract and uterus. The presence of amyloid deposits in these organs was confirmed at autopsy. A review of the literature is given. In amyloidosis, the binding of radionuclide-labeled calcium-seeking agents, such as diphosphonate and pyrophosphate, may be explained by the high calcium content of amyloid. The presence of calcium in amyloid is due to the presence of the non-fibrillar protein, amyloid P-component (AP). In our patient, the amyloid deposits reacted on immunofluorescence with antibodies directed against AP.