Biochemical Micro-Techniques in the Diagnosis and Classification of Amyloidosis

Amyloidosis refers to a heterogeneous group of disorders characterized by the extracellular deposition of amyloid proteins in various tissues of the body. About 25 different amyloid proteins originating from presumably normal precursor proteins have been described so far. Identification of the chemical nature of amyloid is necessary in clinical practice, since both prognosis and treatment regimens are different in the various amyloidoses. This review is aimed at summarizing the new biochemical micro-techniques for precise typing of amyloid proteins in diagnostic biopsy specimens. The reported micro-techniques vary with respect to the state of the amyloid-bearing tissue, i.e., unfixed-frozen or formalin-fixed, the purification strategy (chromatographic or electrophoretic) and the analytical method used (ELISA, Western blotting, amino acid sequencing, mass spectroscopy). The utility and advantages of the described protocols are discussed with regard to tissue state, sample size, amyloid content, simplicity of procedures and possible applicability in diagnostic laboratories.