A chemical classification of amyloid. Correlation with different clinical types of amyloidosis.

Results of recent research have made it possible to classify amyloidosis by means of the chemical and antigenic characteristics of the amyloid fibrils. The chemical classification of amyloid correlates quite well with the various clinical types of amyloidosis. Monoclonal immunoglobulins constitute a major part of primary amyloid fibrils, while amyloid protein AA plays a similar role in secondary amyloidosis. In addition, structural properties of amyloid fibril proteins derived from medullary carcinoma of the thyroid and from senile cardiac amyloidosis respectively, have been shown to be unique for these clinical types of localized amyloidosis. A protein identical or similar to prealbumin appears to constitute an amyloid fibril subunit in familial amyloidotic polyneuropathy. However, the mechanisms by which the various amyloid precursor proteins are converted to fibrils and deposited in the tissues are still not clear.