What is autoimmune hemolytic anemia?
The bone marrow builds about the same number of red blood cells each day. If red blood cells die faster than normally for any reason, the body can compensate for this by accelerating the production of red blood cells up to a certain limit. If the destruction of red blood cells is even faster than this upper production limit, the total number of red blood cells in this patient will decline.
Low numbers of red blood cells are called anemia. While there are many different forms of anemia, like e.g. iron-deficiency anemia, in which the body is unable to build red blood cells fast enough, because it does not get enough iron, the kind where accelerated destruction of red blood cells is causing the number of red blood cells to be low, is called hemolytic anemia, which literally means “blood-dissolving” anemia. Hemolytic anemia has many different causes. The causes fall into two main categories: inherited and acquired. Hereditary (inherited) hemolytic anemia can be caused by problems with the red blood cells themselves and this is called to be caused by “intrinsic” factors. Sickle cell anemia and thallasemia are examples for intrinsic hereditary anemias, where the protein hemoglobin, which transports oxygen and gives the red blood cells its red color, is produced faulty. Other inherited factors that can make red blood cells die faster, are problems with their cell membrane or problems in their cellular metabolism. Unlike other cells in the body, red blood cells rely solely on a metabolic process called glycolysis for energy production, so that deficiencies of enzymes involved in this process can cause problems that lead to inherited hemolytic anemia. These problems can e.g. be caused by inherited glucose-6-phosphate dehydrogenase deficiency or pyruvate kinase deficiency.
Acquired hemolytic anemia can be caused by certain drugs e.g. drugs that inhibit glucose-6-phosphate dehydrogenase, increased activity of the spleen, which can be caused by conditions like portal hypertension ( a condition caused by liver cirrhosis), extensive burns and certain infections. Another important form of hemolytic anemia is called autoimmune hemolytic anemia. In this disease, the immune system, the body’s defense system against foreign intruders like bacteria, viruses and parasites, mistakes the red blood cells for a pathogen, attacks and destroys them. This kind of autoimmune destruction can be found as an isolated disease or, more commonly, as a symptom of other diseases like systemic lupus erythematosus or chronic lymphocytic leukemia in which certain proteins of the immune system called antibodies bind to the red blood cells and signal their destruction. Hemolytic anemia can cause a number of health problems down the road like gall stones, pulmonary hypertension (high blood pressure in the lung), and heart failure.
Signs and symptoms of autoimmune hemolytic anemia
Like all anemias, autoimmune hemolytic anemia causes symptoms of oxygen deprivation to all the cells of the body. The most noticeable signs of this are shortness of breath and fatigue. Pallor is also a common sign of anemia. Decreased red blood cell counts are what define anemias. Another symptom of anemias that is frequently seen in the blood cells is immature red blood cell precursors from the bone marrow that are called reticulocytes. These do not normally show up in large numbers in the blood in healthy people, but they can be seen in chronic anemias, as the bone marrow tries to compensate for the increases red blood cell destruction by increasing their production. In children, this activation and expansion of the bone marrow can even lead to changes in the bone structure that are visible on X-rays.
In healthy people, ageing red blood cell have increasing amounts of a molecule on the outside that signals to spleen cell that the red blood cells are becoming old. The spleen cells then remove the red blood cells from blood stream without releasing any of their contents into the blood. Since in autoimmune hemolytic anemia the red blood cells disintegrate in the blood stream, a lot of their contents can be found in the blood e.g. hemoglobin and hemoglobin breakdown products like bilirubin.
The accumulation of bilirubin and other hemoglobin breakdown products in the blood can be seen as jaundice. Large amounts of bilirubin will be excreted by the liver into the bile ducts, which can cause gall stones. The kidneys also excrete higher than usual amounts of bilirubin and other hemoglobin breakdown products, which can cause the urine to become dark brown. Free hemoglobin in the blood is a risk factor of pulmonary hypertension that can lead to right heart failure, edema (water accumulation), mainly in the lower extremities, and death.
Treatment of autoimmune hemolytic anemia
The main goals of any treatment for hemolytic anemia are to stop or at least decrease the abnormal red blood cell destruction and to increase the red blood cell counts to more normal levels. In the case of autoimmune hemolytic anemias it is vital to treat the underlying condition e.g. in the case of chronic lymphocytic leukemia or systemic lupus erythematosus. If the anemia is so severe that it is life threatening, blood transfusion might be necessary to treat the immediate symptoms.
Plasmapheresis is a procedure that removes antibodies from the blood stream this can help reduce the rate of red blood cell break down as certain autoantibodies bind to outside of the red blood cells and cause them to be either attacked by another defense systems or being removed by specialized immune cells called macrophages. In some cases of autoimmune hemolytic anemia, the offending autoantibodies bind to the red blood cells only in cold temperatures. These are called cold-reactive antibodies. It can be a useful treatment for this condition to avoid cold temperatures and especially to keep fingers, toes, ears, and forehead warm and protected.