The Systemic Amyloidoses

Amyloidosis is not a single disease but a term for diseases that share a common feature: the extracellular deposition of pathologic insoluble fibrillar proteins in organs and tissues. In the mid-19th century, Virchow adopted the botanical term “amyloid,” meaning starch or cellulose, to describe abnormal extracellular material seen in the liver at autopsy.1 Subsequently, amyloid was found to stain with Congo red, appearing red microscopically in normal light but apple green when viewed in polarized light.2,3 Almost a century after Virchow's observations, the fibrillar nature of amyloid was described with the use of electron microscopy and the characteristic beta-pleated–sheet . . .