[Amyloid and amyloidoses].
Amyloid is a pathologic fibrillar aggregation of polypeptides in a cross-beta-sheet conformation. Amyloidoses are caused by the deposition of amyloid and may occur as cerebral and extracerebral disease. More than 29 different amyloid proteins have been identified. Analysis of a Congo red-stained tissue section by polarization microscopy is the gold standard for diagnosing amyloid. Subsequent classification of the amyloid is mandatory and is increasingly supported by molecular biological analyses. In Germany, this recently led to the discovery of several hereditary amyloid diseases. The correct classification of amyloid is of paramount importance. This helps to asses the prognosis and plan patient treatment.