Chromosomal abnormalities in systemic amyloidosis

Primary systemic amyloidosis (AL) is a plasma cell disorder characterized b y deposition of monoclonal light chains in different organ systems. Althoug h multiple and complex numerical chromosomal abnormalities have been descri bed in patients with multiple myeloma, it is currently unknown whether such changes occur in systemic amyloidosis. Bone marrow samples from 21 patients with AL were studied by standard cytog enetics and interphase fluorescence in situ hybridization (FISH) for the pr esence of numerical chromosomal abnormalities. We tested for six chromosome s (7, 11, 9, 15, 18 and X) using centromere-specific probes. The monoclonal plasma cells were identified by simultaneous fluorescent staining of the m onotypic cytoplasmic immunoglobulin. We compared these results with those o btained from 19 patients with monoclonal gammopathy of undetermined signifi cance (MGUS) and normal controls. Multiple numerical chromosomal abnormalities were detected in AL by interph ase FISH, including trisomy of chromosomes 7 (42%), 9 (52%), 11 (47%), 15 ( 39%), 18 (33%) and X (13% in women and 54% in men), Monosomy of chromosome 18 was seen in 72% of cases. Previous exposure to alkylator therapy did not appear to correlate with these abnormalities, No significant difference wa s observed in the prevalence of these abnormalities between AL and MGUS. Multiple chromosomal numerical abnormalities were detected by interphase FI SH analysis in patients with AL, especially monosomy of chromosome 18. Aneu ploidy in the monotypic plasma supports a neoplastic nature for the disorde r.