Fibrinoid dystrophy

Fibrinoid dystrophy is a loss of the fibrous arrangement of collagen and a change in colorability:

Substances staining like fibrin – with HE brick red, with Weigert yellow, with blue trichrome red.
- In fact, it is really fibrin. The name fibrinoid was coined earlier when the true composition of this "fibrin-like substance" was unknown.

Macroscopically, there are no changes. It arises on an autoimmune basis as fibrinoid necrosis:

Interstitial fibrinoid – the focus of necrosis is penetrated by inflammatory exudate in interstitial fibrinous inflammation. Examples:
- rheumatic fever – affecting mainly the heart – pancarditis – when microscopic deposits are formed in the endocardium and myocardium (granulomas – Aschoff's nodules – fibrinoid necrosis in the center, which is surrounded by a border of Aschoff's cells);
- polyarteritis nodosa;
- collagenosis – systemic lupus erythematosus, scleroderma, dermatomyositis.
It is necessary to make the distinction between interstitial fibrinoid and the so-called vascular fibrinoid:
- It occurs in the wall of the arteries (especially the arterioles of the kidneys, spleen and pancreas) if hypertension is present, when plasma penetrates the vessel wall (plasmorhagia) and its protein components (fibrinogen, immunoglobulins) stain as fibrin.

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