Scintigraphic quantification and serial monitoring of human visceral amyloid deposits provide evidence for turnover and regression.

Radiolabelled serum amyloid P component scintigraphy provides information on the diagnosis and distribution of amyloid which was not previously available. A simple reproducible method for quantifying the uptake of 123I-labelled serum amyloid P component into individual livers, spleens and kidneys was devised and evaluated in 22 patients with different types of systemic amyloidosis. Prospective studies in 10 patients were undertaken in order to monitor aspects of the natural history of visceral amyloid deposits. Although measurements of tracer uptake were not as discriminating for diagnostic purposes as the opinions of two highly experienced visual observers, the availability of objective scintigraphic parameters should facilitate interpretation of serum amyloid P component scans in centres unfamiliar with the technique. The follow-up studies demonstrated several intriguing features of amyloidogenesis. There was very rapid progression of deposits in some individuals with differential rates of accretion in different organs. The single patient with AL amyloidosis treated with cytotoxic drugs showed substantial regression of hepatic amyloid deposits whilst his splenic amyloid increased. His spleen was then removed and further regression of the hepatic amyloid was observed. It is concluded that quantitative serum amyloid P component scintigraphy is a useful method for assessing visceral amyloid and that the deposits not only progress at extremely variable rates, but can evidently also be mobilized. These findings encourage active therapeutic approaches in the management of amyloidosis.