The key difference between intravascular and extravascular hemolysis is that in intravascular hemolysis, the destruction of red blood cells within the blood vessels takes place, while in extravascular hemolysis, the destruction of red blood cells elsewhere in the body, mainly in the liver, spleen, bone marrow, and lymph nodes takes place due to the macrophages.
Red blood cells or erythrocytes are the major cellular component in the blood that carries oxygen from the lungs to the tissues. The normal life span of a red blood cell is 120 days. Anemia is a condition that refers to the lack of a sufficient amount of healthy red blood cells in the blood to carry oxygen into body tissues. In other words, it is the condition of low red blood cell counts in the blood. During anemic conditions, blood is unable to carry enough oxygen to tissues. Anemia may occur mainly due to impaired red blood cell production, abnormal red blood cell destruction, fluid overload and blood loss. Hemolysis refers to the destruction of red blood cells, releasing haemoglobin to the surrounding medium. Hemolytic anemia is a type of anemia caused by the abnormal destruction of red blood cells. It can occur in two ways as intravascular or extravascular.
CONTENTS
1. Overview and Key Difference
2. What is Intravascular Hemolysis
3. What is Extravascular Hemolysis
4. Similarities – Intravascular and Extravascular Hemolysis
5. Intravascular vs Extravascular Hemolysis in Tabular Form
6. Summary – Intravascular vs Extravascular Hemolysis
What is Intravascular Hemolysis?
Intravascular hemolysis is one of the two types of hemolysis in haemolytic anemia. The red blood cells within blood vessels are destroyed in intravascular hemolysis. This causes the release of haemoglobin into plasma, leading to hemoglobinuria. It is also responsible for the occurrence of hemoglobinemia. Intravascular hemolysis may occur due to enzyme defects and certain immune-mediated processes. Autoantibodies can target red blood cells and destroy them. Moreover, some parasites can damage red blood cells.
Figure 01: Hemolytic Anemia
What is Extravascular Hemolysis?
Extravascular hemolysis is the second mechanism of hemolysis that causes haemolytic anemia. In extravascular hemolysis, red blood cell destruction takes place mainly in the liver, spleen, bone marrow, and lymph nodes. As a result, haemoglobin escapes into the blood plasma.
Figure 02: Extravascular Hemolysis
In this mechanism, macrophages in the reticuloendothelial system detect defective red blood cells, engulf and destroy them. Spleen destroys mildly abnormal red blood cells while the liver destroys severely defective red blood cells, which are coated by antibodies. Therefore, extravascular hemolysis is mainly driven by the spleen and liver in order to remove damaged or abnormal RBCs from circulation.
What are the Similarities Between Intravascular and Extravascular Hemolysis?
- Intravascular and extravascular hemolysis are two types of mechanisms of hemolysis in haemolytic anemia.
- In both conditions, haemoglobin escapes into blood plasma due to the destruction of red blood cells.
- Due to both conditions, the ability of blood to carry oxygen into body tissues decreases.
- Both can occur due to immune-mediated processes.
What is the Difference Between Intravascular and Extravascular Hemolysis?
Intravascular hemolysis is a type of hemolysis in which the destruction of red blood cells within the blood vessels takes place. In contrast, extravascular hemolysis is a type of hemolysis in which the destruction of red blood cells in the liver, spleen, bone marrow, and lymph nodes takes place by macrophages. So, this is the key difference between intravascular and extravascular hemolysis. Moreover, intravascular hemolysis occurs due to enzyme defects and certain immune-mediated processes while extravascular hemolysis occurs when defective red blood cells are engulfed and destroyed by the macrophages.
The following table summarizes the difference between intravascular and extravascular hemolysis in tabular form.
Summary – Intravascular vs Extravascular Hemolysis
Intravascular and extravascular hemolysis are two mechanisms by which hemolysis takes place. Red blood cells within the blood vessels are destroyed in intravascular hemolysis. Red blood cells elsewhere in the body, such as the liver, spleen, bone marrow, etc., are destroyed in extravascular hemolysis. Spleen and liver clear out damaged or defective red blood cells from the circulation by extravascular hemolysis. Intravascular hemolysis occurs due to enzyme defects, toxins, autoimmune processes, trauma, etc. Thus, this is the summary of the difference between intravascular and extravascular hemolysis.
Reference:
1. Evan M. Braunstein, et al. “Overview of Hemolytic Anemia – Hematology and Oncology.” MSD Manual Professional Edition, MSD Manuals.
2. “Mechanisms.” EClinpath.
Image Courtesy:
1. “Modified sickle cell 01” By NHLBI – (Public Domain) via Commons Wikimedia
2. “Brisk Extravascular Hemolytic Anemia” Ed Uthman (CC BY 2.0) via Flickr