Renal amyloidosis (part I)

The term amyloidosis refers to the deposition of an amorphous substance defined by the presence of a fibrillar structure by electron microscopy and a characteristic beta-pleated sheet structure by x-ray diffraction. The existence of this group of diseases has been recognized for centuries, but major advances in the elucidation of the nature of the deposits have been achieved in the past few years. It is now recognized that the beta-sheet configuration responsible for the general appearance of amyloid deposits is common to a large array of proteins with a different origin. This tertiary structure is responsible for the characteristic tinctorial and optical properties evident by Congo red staining. The material that accumulates in the extracellular compartment progressively destroys the involved organ. The accumulation of amyloid deposits may complicate the course of a wide variety of diseases. Classifications of amyloid disorders reflect some of the current concepts concerning the protein composition of amyloid fibrils in different diseases.