摘要：

he amyloidoses constitute a large group of diseases in which misfolding of extracellular protein has a prominent role. This dynamic proc- ess, which occurs in parallel with or as an alternative to physiologic folding, generates insoluble, toxic protein aggregates that are deposited in tissues in bundles of b -sheet fibrillar protein (Fig. 1). (A b -sheet consists of strands of polypeptides in zigzag formation, as shown in Fig. 2.) These amyloid deposits are identified on the ba- sis of their apple-green birefringence under a polarized light microscope after staining with Congo red and the presence of rigid, nonbranching fibrils 7.5 to 10 nm in diameter, on electron microscopy (Fig. 2). 1 Amyloid deposits are the basis of several conditions that have an enormous social and medical impact as well as the cause of rare condi- tions that challenge the physician's diagnostic capability (Table 1). The deposition of amyloid in brain tissue underlies Alzheimer's disease, 2,3 which affects more than 12 million people worldwide. The central nervous system is also the target of prion proteins, the cause of a group of rare hereditary or acquired neurode- generative conditions. 4 The approximately 1 million patients who are receiving dialysis worldwide are at risk for symptomatic amyloidosis. 5 The two most common forms of systemic amyloidosis are light-chain (AL) amyloidosis, with an incidence of approxi- mately 1 case per 100,000 person-years in Western countries, 6 and reactive amyloidosis due to chronic inflammatory diseases (e.g., rheumatoid arthritis and chronic infections). Hereditary amyloidosis is an ever-expanding group of disorders that pose difficult di- agnostic problems. 7 The clinical features of systemic amyloidosis were reviewed in the Journal in 1997. 8

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