How are the amyloidoses classified?
By the major protein component of the fibril. This has also become the basis for defining the clinical syndromes with certainty. However, routine stains do not identify the major fibril protein, and specific immunohistochemical stains are needed for identification
Classification of Amyloidoses
| Clinical Categories | Major Protein Types | Relative Frequencies (%) |
|---|---|---|
| Systemic AL amyloidosis | AL | 50–80 |
| Systemic AA amyloidosis | AA | 3–10 |
| Age-related (senile) systemic amyloidosis | AATR | 8–10 |
| Organ-specific (localized) amyloidosis | AL, ALECT2, and others a | 3 |
| Dialysis-related amyloidosis | Aβ 2 M | – |
| Heritable amyloidosis | ATTR and others b | 5–10 |
a Other organ-specific (localized): ALECT2, leukocyte cell-derived chemotaxin 2 – hepatic amyloid; Aβ, amyloid β protein – Alzheimer’s disease, Down syndrome; AIAPP, islet amyloid polypeptide – type 2 diabetes, insulinoma; ACal, calcitonin – medullary thyroid cancer; AANF, atrial natriuretic factor – atrial amyloid; AMed, lactadherin – aortic media; ALac, lactoferrin – cornea; others.
b Other hereditary (familial): AApoA, apolipoprotein AI and AII; AGel, gelsolin; AFib, fibrinogen A alpha; ALys, lysozyme; ACys, cystatin C.
