Fibrinoid necrosis

August 29, 2023

Fibrinoid necrosis is a specific type of tissue necrosis (cell death) characterized by the accumulation of fibrin-like material in the extracellular space within the tissue. This form of necrosis typically occurs in response to immune-mediated vascular injury, where complexes of antigens and antibodies deposit in the walls of blood vessels, leading to acute inflammation and damage. The term “fibrinoid” refers to the fiber-like appearance of the necrotic material, which resembles fibrin, a protein involved in blood clotting.

Common causes of fibrinoid necrosis

Fibrinoid necrosis is often associated with:

• Immune reactions: Particularly those involving immune complexes (antigen-antibody complexes) that deposit in the walls of blood vessels, leading to vasculitis (inflammation of the blood vessels). This is seen in autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and polyarteritis nodosa.
• Hypertensive emergencies: Severe increases in blood pressure can cause damage to blood vessel walls, leading to fibrinoid necrosis.
• Pre-eclampsia: A condition in pregnancy characterized by high blood pressure and often associated with damage to the placental vessels.
• Certain infections: That lead to severe inflammatory responses can also cause fibrinoid necrosis.

Microscopic appearance of fibrinoid necrosis

Under the microscope, fibrinoid necrosis appears as a homogenous, pink (eosinophilic), and amorphous (structureless) deposit within the walls of blood vessels or in the extracellular space. This appearance is due to the presence of fibrin and other plasma proteins, along with necrotic cellular debris. The affected area lacks the typical cellular structure of healthy tissue and instead shows this distinctive, brightly eosinophilic (due to eosin staining) material. Staining techniques, such as those using hematoxylin and eosin (H&E), highlight the contrast between the pink, amorphous fibrinoid material and the surrounding tissue structures.

In diseases affecting blood vessels, such as vasculitis, fibrinoid necrosis can lead to the weakening of the vessel walls, potentially causing hemorrhage or thrombosis (blood clots), which can further impair organ function. The presence of fibrinoid necrosis is an important diagnostic feature in certain pathological conditions, providing insight into the disease process and guiding treatment decisions.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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