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DEFINITION

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  • Amyloidosis is a clinical syndrome resulting from disorders of secondary protein structure, in which a precursor protein is secreted from the cell in a soluble form, only to become insoluble at some tissue site, ultimately compromising organ function.

  • The term amyloid is used to describe a substance with a homogeneous eosinophilic appearance by light microscopy, a green birefringence on polarizing electron microscopy, and a characteristic β-pleated sheet appearance by x-ray diffraction.

  • Terms such as primary, secondary, senile, dialysis-associated, and myeloma-associated have been abandoned in favor of the etiologically based, chemical terminology (Table 72–1) (e.g., immunoglobulin light chain amyloidosis is termed AL amyloidosis).

  • The incidence of AL amyloidosis is approximately 4.5 per 100,000 persons in the United States.

  • Amyloid A (AA) amyloidosis is increasingly rare, occurring in less than 1 percent of persons with chronic inflammatory diseases in the United States and Europe.

  • AA amyloidosis is more common in Turkey and the Middle East, where it occurs in association with familial Mediterranean fever.

  • AA is the only type of amyloidosis that occurs in children.

  • Amyloid β2-microglobulin (Aβ2M) amyloidosis usually manifests as deposits in the joint synovial and occurs in patients on long-term dialysis.

    — Aβ2M amyloidosis is also declining in incidence with changes in dialysis techniques.

  • The inherited amyloidoses are rare in the United States, with an estimated incidence of less than approximately 1 per 100,000 persons.

  • Amyloidogenic transthyretin (ATTR) amyloidosis is the most common form of familial amyloidosis and is associated with mutations of the gene encoding transthyretin (TTR).

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Table Graphic Jump Location
TABLE 72–1THE MODERN (CHEMICAL) CLASSIFICATION OF HUMAN AMYLOIDOSIS

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