Todayโs path rounds are on ๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐๐จ๐ฌ๐ข๐ฌ!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐๐จ๐ฌ๐ข๐ฌ is caused by a group of diseases that result in high levels of ๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐ being deposited in the tissues. Amyloid is a protein material that has a characteristic folding pattern, but has many forms produced in many different situations.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Any species can get this!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
The most common causes of amyloidosis are inflammation and certain types of tumours. In humans, we also see it associated with Alzheimerโs.
Inflammation causes amyloidosis by producing large amounts of ๐๐ ๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐, which is derived from ๐ฌ๐๐ซ๐ฎ๐ฆ ๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐ ๐. SAA is an ๐๐๐ฎ๐ญ๐ ๐ฉ๐ก๐๐ฌ๐ ๐ฉ๐ซ๐จ๐ญ๐๐ข๐ง, which is a group of proteins produced during inflammation. SAA is broken down in to AA amyloid, so when there is chronic inflammation leading to large amounts of SAA, AA amyloid can accumulate.
๐๐ ๐๐ฆ๐ฒ๐ฅ๐จ๐ข๐ is produced by tumours of ๐ฉ๐ฅ๐๐ฌ๐ฆ๐ ๐๐๐ฅ๐ฅ๐ฌ, which are the cells that produce antibodies. Antibodies are made up of ๐ฅ๐ข๐ ๐ก๐ญ ๐๐ก๐๐ข๐ง๐ฌ, so when there is a plasma cell tumour with tons of antibodies produced, these light chains can accumulate in large numbers.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Amyloid tends to accumulate in the kidney and liver, causing expansion of these tissues by take up space in the organ. Eventually, this can lead to pressure ๐ง๐๐๐ซ๐จ๐ฌ๐ข๐ฌ (cell death), which often heals by scarring. If enough of the organ is affected, you may see signs of liver failure or kidney failure.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Amyloidosis is typically diagnosed on biopsies or at necropsy. The tissue will generally look quite pale and have a waxy texture, due to the accumulation of the protein. A fun magic trick that pathologists might try is applying ๐๐ฎ๐ ๐จ๐ฅ’๐ฌ ๐ฌ๐ญ๐๐ข๐ง to the tissue, which will stain the amyloid dark brown, and make it easy to identify!
On histology, amyloid has more fun colour changing properties. When a ๐๐จ๐ง๐ ๐จ ๐ซ๐๐ stain is applied to the tissue sample, the tissue will glow ๐๐ฉ๐ฉ๐ฅ๐ ๐ ๐ซ๐๐๐ง under polarized light. Funky!
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Unfortunately there is no specific treatment for amyloidosis, other than identifying and treating the underlying cause.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-2) A sample of a kidney and a liver with amyloidosis.
3-4) Kidneys with Lugolโs stain applied!
5-7) What amyloid looks like under our typical stain, H&E, then under Congo Red with normal light, and then under polarized light.
8-9) Another Congo Red and polarized light example!
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 2. Sixth Edition.
Photos 1-4, 8-9 ยฉ Noahโs Arkive contributors King, McGavin, Read, Williams, Crowell licensed under CC BY-SA 4.0.
Photos 5-7ยฉ University of Calgary Diagnostic Services Unit.
