Immune-mediated hemolytic anemia (IMHA) is a type of anemia that occurs when the body's own immune system mistakenly attacks and destroys red blood cells. The body's immune system produces antibodies that attach to red blood cells, causing them to agglutinate and be destroyed by the spleen. The result is a decrease in the number of red blood cells, leading to anemia.
Pathogenesis
The exact cause of IMHA is not known, but it is thought to be triggered by infections, drugs, toxins, or other underlying conditions. There are two types of IMHA - primary and secondary. Primary IMHA is thought to be caused by an autoimmune reaction, whereby the body's immune system mistakenly attacks its own red blood cells. Secondary IMHA is caused by an underlying condition or other trigger, such as an infection or drug reaction.
Autoantibodies are antibodies that are produced by the body against its own cells or tissues. In IMHA, autoantibodies are produced against red blood cells, causing them to agglutinate and be destroyed by the spleen. The autoantibodies may be IgG, IgM, or both.
Complement activation is another mechanism that is thought to be involved in IMHA. Complement is a system of proteins in the blood that is involved in the body's immune response. In IMHA, complement is activated, leading to the formation of a membrane attack complex (MAC) on the red blood cell surface. This leads to the destruction of the red blood cell.
Inflammation is another mechanism that may be involved in the pathogenesis of IMHA. Inflammation occurs when the body's immune system mounts a response against a perceived threat. In IMHA, inflammation can lead to the destruction of red blood cells as well as the release of inflammatory mediators.
Genetic factors may also be involved in the pathogenesis of IMHA. There are some rare genetic disorders that are associated with IMHA, such as paroxysmal nocturnal hemoglobinuria (PNH).
Hypercoagulability is another mechanism that may be involved in IMHA. Hypercoagulability is a state in which the blood is more likely to clot than normal, which can lead to the formation of clots in the small vessels of the spleen, leading to the destruction of red blood cells.
These are some of the mechanisms that are thought to be involved in the pathogenesis of IMHA. More research is needed to better understand the underlying causes of this condition.
