Fibrinoid necrosis

Fibrinoid necrosis is a specific type of tissue damage characterized by the buildup of fibrin-like material in tissues, especially within blood vessel walls. It usually occurs when blood vessels become severely injured due to immune reactions or high blood pressure. The name “fibrinoid” comes from its similarity to fibrin, a protein normally involved in blood clotting.

What causes fibrinoid necrosis?

Fibrinoid necrosis typically occurs in response to specific types of injury or inflammation.

Common causes include:

• Immune reactions: Conditions where the immune system mistakenly attacks blood vessel walls, causing inflammation (vasculitis). Examples include autoimmune diseases like systemic lupus erythematosus (SLE), rheumatoid arthritis, and polyarteritis nodosa.
• Severe high blood pressure: Extremely high blood pressure can damage blood vessel walls, leading to fibrinoid necrosis.
• Pre-eclampsia: A pregnancy-related condition characterized by high blood pressure, often resulting in damage to the placental blood vessels.
• Severe infections: Certain infections can cause intense inflammation, leading to fibrinoid necrosis.

What does fibrinoid necrosis look like under the microscope?

Under a microscope, fibrinoid necrosis appears as bright pink, structureless deposits within or around blood vessel walls. These deposits contain fibrin, plasma proteins, and cellular debris, resulting in the affected area having a distinctive, smooth, and amorphous appearance. Pathologists use special stains, such as hematoxylin and eosin (H&E), to highlight the fibrinoid material, making it easier to see clearly against normal surrounding tissues.

Why is fibrinoid necrosis important?

Fibrinoid necrosis weakens blood vessel walls, which can lead to serious complications like bleeding (hemorrhage) or blood clots (thrombosis). These complications can disrupt blood flow and damage organs, affecting their ability to function properly. Identifying fibrinoid necrosis helps pathologists diagnose certain conditions, understand the severity of the disease, and guide appropriate treatments.