SERUM AMYLOID-P COMPONENT SCINTIGRAPHY AND TURNOVER STUDIES FOR DIAGNOSIS AND QUANTITATIVE MONITORING OF AA-AMYLOIDOSIS IN JUVENILE RHEUMATOID-ARTHRITIS

Objective. To evaluate aspects of the natural history of AA amyloidosi s complicating juvenile rheumatoid arthritis (JRA), and its response t o therapy with chlorambucil. Methods. Scintigraphy and 7-day turnover studies were performed in JRA patients with histologically proven (n = 35) or clinically suspected (n = 30) AA amyloidosis, following intrav enous injection of I-123 and I-125-labeled serum amyloid P component ( SAP). Prospective monitoring studies were performed over 2-3 years in 20 patients with amyloidosis. Atl but 2 amyloidosis patients were trea ted with chlorambucil. Results. Positive scanning results were obtaine d in all patients in whom imaging was performed within 12 years of pos itive biopsy findings of amyloid and in 5 patients with clinically sus pected amyloidosis. Negative scanning results with normal SAP metaboli sm, indicating regression of amyloid, were obtained in 4 patients whos e amyloidosis had been in full clinical remission for more than 12 yea rs. Prospective monitoring studies in patients whose JRA-associated in flammatory activity was in remission demonstrated regression of amyloi d in 8 patients and no substantial changes in 8 others; however, in 4 further patients with active inflammation, there was accumulation of a myloid. There was a very poor correlation between the amount of amyloi d present at a particular site and the resultant organ dysfunction. Co nclusion. Radiolabeled SAP scintigraphy and turnover studies are usefu l complementary toots in the diagnosis, screening, and quantitative mo nitoring of type AA amyloidosis in JRA. The amyloid deposits may progr ess and/or regress at different rates in different anatomic sites over short periods.