Mass spectrometry (MS)-based proteomics can directly identify amyloid deposits. We describe successful proteomic amyloid typing in fat aspirates in which immunoelectron microscopy (IEM) had not provided conclusive results. Samples with amyloid fibrils not labeled by the antibodies used in IEM were referred for 2D-PAGE-based comparative proteomics. Spots unique for patients were analyzed by matrix-assisted laser desorption/ionization time of flight MS and database search. IEM could not characterize fibrils in 2/360 cases analyzed in 2009. In both, 2D gels displayed novel spots. Patient 1 had cardiac amyloidosis, a serum monoclonal IgM(lambda; high λ FLC, and free μ heavy chains. MS allowed to assign the spots to the monoclonal λ LC sequenced from bone marrow. Patient 2 had cardiac, renal, and GI amyloidosis, high κ FLC, and a κ band at serum immunofixation. MS and database search identified the spots as a κ LC. Proteomics is a useful diagnostic complement when IEM fails in amyloid typing.
ASJC Scopus subject areas
- Internal Medicine