Cells with clonal light chains are present in peripheral blood at diagnosis and in apheretic stem cell harvests of primary amyloidosis

In primary systemic amyloidosis, small numbers of bone marrow plasma cells secrete monoclonal light chains that form extracellular fibrils (amyloid) i n various organs. Evidence limited to a few cases suggests that rare clonal elements can also be found in the peripheral blood (PB), and this may be r elevant in PB stem cell autotransplantation. Since up to 40% of amyloid clo nes do not synthesize heavy chains, in order to detect tumor cells with hig h specificity and sensitivity we developed a seminested allele-specific oli gonucleotide polymerase chain reaction for tumor light chains. Clone-relate d sequences were detected in DNA and/or cDNA from the PB cells of eight of 10 patients at diagnosis and from apheretic collections of three of four ca ses undergoing PB progenitor autotransplantation. Since there are experimen tal data suggesting that circulating tumor cells may be involved in the gro wth of the amyloidogenic clone and may be chemoresistant, these findings ar e relevant to the use of leukapheresis purging strategies for PB progenitor autotransplantation in amyloidosis.