Hyaline material vs hyalinosis versus fibrinoid necrosis...

[CBG23]

So, I am a bit confused about the difference between hyaline material, hyalinosis, and fibrinoid necrosis. I looked up the terms in both Robbins and Rubin's Pathology and it seems like hyaline material can refer to any eosinophilic staining material. In Robbins, hyalinosis is defined as homogenous pink staining material that is caused by vessel damage that causes movement of plasma proteins from the blood through the endothelium to get trapped within the vessel wall. In Robbins, fibrinoid necrosis refers to bright eosinophilic staining material composed of plasma proteins (including fibrin) that gets stuck in the vessel wall after immune complex mediated vessel damage. In Rubin's it says that fibrinoid necrosis is caused by vessel damage that leads to plasma proteins getting stuck in the vessel wall and staining bright pink on H&E.

It seems as if hyalinosis and fibriboid necrosis are basically the same thing, but thing different terms are used for different diseases:

Arteriolar damage seen in hypertension --> hyalinosis
Polyarteritis nodosa --> fibrinoid necrosis
Focal Segmental Glomerulosclerosis --> hyalinosis
Glomerulonephritis seen with Microscopic Polyangiitis --> fibrinoid necrosis

Maybe it doesn't really matter, but it's bugging the hell out of me because no source I have looked at has very clearly distinguished between the two, but they are selective used for certain diseases. Anyone have any insight?

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[rankin]

Please correct me if I am wrong. But whereas hyaline is a glassy pink staining substance fibrinoid necrosis deposits can often stain purple or blue because of entrapped DNA from necrotic cells. Also hyaline simply describes the deposition of a proteinaceous material whereas fibrinoid necrosis refers to the associated cell death and typical features of a necrosis (membrane rupture/nuclear disintegration etc.).

 

[CBG23]

I didn't know that - all of the images I've seen in Robbins and in other path books just shows purely eosinophilic material. According to Rubin's "the term is somewhat of a misnomer because the eosinophilia of the accumulated plasma proteins obscures the underlying alterations in the blood vessel, making it difficult, if not impossible, to determine whether there is truly necrosis in the vascular wall."

 

[rankin]

The necrosis may or may not be detectable that is true but is irrelevant to the meaning of the term. When you say hyaline deposits or accumulation, necrosis is not part of the picture but when you know there is 'hyaline-like' material which as I said before might not necessarily be pink and as homogenous as true hyaline as well as necrosis from say vasculitic disease then it is termed fibrinoid necrosis.

Refer to this picture and description and how its a pink material with fibrin like quality as oppose to glassy homogenous hyaline.

http://library.med.utah.edu/WebPath/ATHHTML/ATH023.html

Of course hyaline can appear to be identical and might be used interchangeably and rightly so because hyaline is a composition of a variety of proteins but sometimes you can probably make the distinction. The key I think is to know that fibrinoid is fibrin leaking from the basement membrane + all the complex deposition whereas as hyaline is any pink homogenous glassy material that may be a result of plasma protein or some other pathology like alcoholic liver and mallory's hyaline.

 

[CBG23]

Makes sense now - thanks!