Amyloidosis

In amyloidosis, “amyloid” refers to starch-like, and it goes back to an observation made by the German scientist Rudolf Virchow, who saw mysterious deposits in the tissue that stained blue with iodine, just like plant starch.

As it turns out, amyloids are actually just proteins that take on an abnormal shape, which makes them stick together and settle in tissues.

And amyloidosis is the name for the disease that develops as a result of the tissue damage from these protein deposits.

Normally, our cells produce thousands of proteins each and every moment, and these proteins need to fold into a particular shape in order to do their jobs properly.

If a protein folds incorrectly, it’s normally spotted right away and destroyed by proteases, which are enzymes that chop up larger proteins into tiny bits.

In amyloidosis, there are a few different ways that protein folding can go wrong.

One way is when normal proteins are produced in enormous amounts, and just a small fraction of them fold incorrectly.

A second option is that abnormal proteins with incorrect amino acid sequences are produced in normal amounts, and they fold incorrectly.

Either way, the misfolded proteins, called amyloids start to build up.

Sometimes there’s simply too many of them for the protease to handle, and other times, the way that they’re folded makes them tough to break down - a bit like a pistachio that doesn’t have an opening for your fingers to work with. Nightmare.

When the amyloid proteins get excreted out of the cell, they tend to clump together forming a rigid, insoluble structure called a β-sheet - like a folded sheet of paper.

These β- sheets then deposit in the extracellular space of tissues and cause damage.

So amyloidosis is a process where there are extra protein deposits, and there are many different proteins and diseases that follow that same underlying process.

In general, amyloidosis can be systemic, meaning that those protein deposits occur in multiple organ systems, or it can be localized, meaning that they occur in one organ.

Until recently, systemic amyloidosis was further broken down into primary amyloidosis, which is where amyloidosis was thought to be the main problem, and secondary amyloidosis, which is where there was another known disease process that resulted in the protein deposits.

However, this is not totally accurate, since an underlying disease process has been identified even in the primary form.

OK, so, AL amyloidosis, previously known as primary amyloidosis, is where “A” refers to amyloidosis and “L” refers to the immunoglobulin light chain as the protein that gets misfolded and deposited.