Overview of systemic and localized amyloidosis

Amyloidosis is a family of protein misfolding disorders, in which insoluble fibrillar proteins deposit extracellularly and cause end organ damage. Depending on the precursor protein, clinical manifestations in amyloidosis vary significantly. In systemic amyloidosis, the heart, kidneys, and nerves are most commonly affected, resulting in congestive heart failure, arrhythmia, nephrotic syndrome, renal failure, and peripheral and autonomic neuropathies. In localized amyloidosis, amyloid deposits at the site of production, so only one organ is disrupted. Once amyloidosis is confirmed histologically, the precursor subtype must be identified using immunohistochemistry, immunofixation, electron microscopy, or laser microdissection and mass spectrometry. Treatment should not be initiated prior to the identification of the type of amyloidosis. Currently, treatment focuses on the suppression of the precursor protein: in AL amyloidosis, chemotherapy or autologous stem cell transplants suppress production of immunoglobulin light chains; in AA amyloidosis, anti-microbial and anti-inflammatory agents suppress amyloid A production; and in AF amyloidosis, a liver transplantation removes the source of mutant transthyretin protein production. Newer drugs are being developed to target amyloidosis at an epigenetic level or stabilize folding intermediates, but there are currently in development.