Key Information
Source
Year
2024
summary/abstract
Introduction
Amyloid is the product of misfolded proteins that when deposited causes organ failure and eventually death.1external link, opens in a new tab Currently, 42 proteins are recognized as amyloidogenic in humans.2external link, opens in a new tab The most serious forms are those that involve vital organs such as heart, liver, and kidney.3external link, opens in a new tab The pattern of organ involvement is type specific, but the kidney is the vital organ most commonly involved.2external link, opens in a new tab The purpose of this review is to provide an update on the amyloids that involve the kidney and typing of renal amyloidosis.
Amyloidosis is named after the native protein and is often classified by whether it is wild type (acquired) or the result of a germline pathogenic variant (mutant).2external link, opens in a new tab Currently, 6 amyloidogenic proteins can form amyloid both as a wild-type or mutant protein: transthyretin (ATTR), β2-microglobulin (AB2M), serum amyloid A (AA), and apolipoprotein A-IV (ApoAIV), Aβ protein (Aβ), and prion (APrP) (Fig 1external link, opens in a new tab); only the first 4 affect the kidney.2external link, opens in a new tab,4external link, opens in a new tab Of the 4 iatrogenic amyloids that appear as subcutaneous nodules at the injection sites,2external link, opens in a new tab AIL1RAP (interleukin-1 receptor antagonist [anakinra]) was recently found to have kidney involvement.5external link, opens in a new tab,6external link, opens in a new tab Kidney involvement was reported in 1 tumor-related amyloid calcitonin (ACal).7external link, opens in a new tab Finally, the pathogenesis of leukocyte cell–derived chemotaxin 2 amyloidosis (ALECT2) remains incompletely understood.
Pathology of Renal Amyloidosis
The diagnosis of amyloidosis requires a tissue biopsy. Common amyloid characteristics on light microscopy, immunofluorescence, electron microscopy, and Congo red staining are illustrated in Figure 2external link, opens in a new tab.8-10external link, opens in a new tab In early cases, Congo red can be negative, with a very small amount of glomerular amyloid.11external link, opens in a new tab Thioflavin T produces yellow green fluorescence on binding to amyloid and is more sensitive in detecting small amount of amyloid. However, it is less specific than Congo red and presently is rarely used in pathology practice.12external link, opens in a new tab