MONOCLONAL ORIGIN OF LOCALIZED ORBITAL AMYLOIDOSIS DETECTED BY MOLECULAR ANALYSIS

Aims - Primary localised orbital amyloidosis is a rare disease. The pu rpose of this study was to describe two cases of primary orbital amylo idosis and emphasise the value of molecular analysis of immunoglobulin gene rearrangement in identifying a monoclonal population of cells re sponsible for the amyloid production. Methods - Charts and biopsy spec imens of each case were reviewed. Conventional light microscopy, immun ohistochemistry, and polymerase chain reaction (PCR) analysis for immu noglobulin gene rearrangement were performed in both cases. Results - An unusual presentation of localised primary amyloidosis with bilatera l and extensive enlargement of multiple extraocular muscles was seen i n case 1. The presence of amyloid deposits was confirmed by biopsy in both cases. Evidence of a monoclonal, population of plasma cells was s hown by immunohistochemical analysis in case 2 only. The monoclonal or igin of the cells responsible for the amyloid deposition was determine d by PCR analysis demonstrating immunoglobulin heavy chain gene rearra ngement in both cases. Conclusions - A monoclonal population of plasma cells responsible for the amyloid deposition was present in these two cases. PCR analysis is extremely helpful in determining monoclonality , a finding that may have important therapeutic and prognostic implica tions.