Endotheliitis refers to the inflammation of the endothelium, a single layer of cells that lines the inner surface of blood vessels and other organs throughout the body. This delicate lining plays a significant role in maintaining health. When the endothelium becomes inflamed, its normal functions are disrupted, which can lead to various health implications. Understanding this condition involves recognizing the widespread impact of endothelial inflammation.
What is Endotheliitis?
The endothelium is a thin, single layer of flattened endothelial cells that forms the inner surface of all blood and lymphatic vessels. This extensive lining functions as more than just a barrier; it is an active organ regulating numerous physiological processes. Endothelial cells secrete substances that control the opening and closing of blood vessels, influencing blood pressure and blood flow. They also regulate the exchange of fluids and electrolytes, contribute to blood clot formation, and prevent toxins from entering tissues.
When endotheliitis occurs, these endothelial cells become inflamed, impacting their ability to perform these functions. At a microscopic level, inflammation can cause endothelial cells to activate, leading to the expression of adhesion molecules on their surface. This activation also prompts the release of pro-inflammatory cytokines and chemokines, which can attract immune cells and intensify the inflammatory response within the vessel walls. Such inflammation disrupts the endothelium’s integrity, potentially leading to increased permeability, impaired blood flow, and the formation of small blood clots, which can ultimately compromise the function of the tissues and organs they supply.
Common Causes and Associated Conditions
Endotheliitis can arise from various underlying factors, broadly categorized into infectious and non-infectious origins. Infectious agents are common culprits, with viruses being particularly common. Herpes simplex virus (HSV), cytomegalovirus (CMV), and varicella zoster virus (VZV) are well-documented causes, especially in cases affecting the eyes. Emerging evidence also points to viruses like SARS-CoV-2, responsible for COVID-19, as direct triggers of systemic endotheliitis. While certain bacteria can cause general inflammation in tissues, isolated bacterial endotheliitis is less frequently reported.
Autoimmune diseases represent another category of causes, where the body’s immune system mistakenly attacks its own endothelial cells. An example is allograft rejection following corneal transplantation, where the immune system attacks donor corneal tissue. Conditions like Sjögren’s syndrome, an autoimmune disorder, can also involve inflammation that impacts endothelial health. Less common triggers include certain medications, toxins, or exposure to animal venoms.
How Endotheliitis Affects the Body
The systemic impact of endotheliitis stems from the widespread nature of the endothelium. When endothelial function is compromised, it can lead to various symptoms and complications depending on the affected organ system. This inflammation can disrupt microcirculation, cause tissue swelling, and promote a tendency for blood clot formation, leading to reduced blood flow and potential damage to organs.
In the eyes, endotheliitis often manifests as corneal endotheliitis, characterized by swelling of the cornea, inflammatory deposits on the inner corneal surface, and inflammation within the front part of the eye. Patients may experience eye pain, sensitivity to light, and blurred vision, with severe cases potentially leading to permanent vision loss due to persistent corneal swelling. Beyond the eyes, widespread endotheliitis can affect the cardiovascular system, increasing the likelihood of blood clots, strokes, heart attacks, and high blood pressure. In conditions like severe COVID-19, systemic endotheliitis contributes to hyperinflammation and a tendency for clotting, which can result in acute respiratory distress syndrome and widespread organ damage, including the heart, kidneys, and liver.
Diagnosis and Management
Diagnosing endotheliitis involves a combination of clinical assessment, specialized imaging, and laboratory tests. A healthcare provider will evaluate a patient’s symptoms, which might include eye pain, visual changes, or signs of systemic inflammation. For suspected corneal endotheliitis, an eye examination often reveals corneal swelling and characteristic deposits on the inner corneal surface.
Imaging techniques like specular microscopy can assess the density and health of endothelial cells, revealing changes in cell size or shape. In vivo confocal microscopy provides detailed, real-time images of the corneal layers, helping to identify specific features associated with endotheliitis. Laboratory tests, particularly polymerase chain reaction (PCR) analysis of fluid samples from the affected area, are often used to identify specific viral causes like CMV, HSV, or VZV. Blood tests might also be conducted to check for general inflammatory markers or specific antibodies if an autoimmune cause is suspected.
Management strategies for endotheliitis focus on addressing the underlying cause and controlling inflammation. For viral endotheliitis, antiviral medications are prescribed. When an autoimmune process is identified, immunosuppressive medications, such as corticosteroids, are administered to reduce the immune response. Corticosteroids are also used to manage inflammation in infectious cases, often combined with antivirals and not used as a standalone treatment. Prompt diagnosis and a tailored treatment approach are important to minimize endothelial cell damage and prevent long-term complications, such as persistent corneal swelling or organ failure.