Chemical typing of amyloid protein contained in formalin-fixed paraffin-embedded biopsy specimens

The human amyloidoses represent a heterogeneous group of disorders characte rized by the deposition of fibrillar protein in vital organs. Given the fac t that at least 20 different molecules can form fibrils, the unambiguous id entification of the type of amyloid deposited is critical to the correct di agnosis and treatment of patients with these disorders. Heretofore, this in formation has been inferred from particular clinical features of the diseas e, ancillary laboratory tests, and results of immunohistochemical analyses. However to establish unequivocally the kind of protein that is deposited a s amyloid, it is necessary to deter-mine its chemical composition through a mino acid sequencing or mass spectroscopy of material extracted from fibril lar deposits. We have developed a micromethod whereby such studies can be p erformed readily using sections of formalin-fixed, paraffin-embedded biopsy specimens. The ability to identify precisely the nature of the tissue depo sits has diagnostic therapeutic and prognostic implications for patients wi th amyloid-associated disorders.