Anemia describes the condition in which the number of red blood cells in the blood is low. For this reason, doctors sometimes describe someone with anemia as having a low blood count. A person who has anemia is called anemic.
Blood is comprised of two parts; a liquid part called the plasma and a cellular part. The cellular part contains several different cell types. One of the most important and most numerous types and the most numerous cell type are red blood cells. The other cell types are the white blood cells and platelets. Only red blood cells are discussed in this article. The purpose of the red blood cell is to deliver oxygen from the lungs to other parts of the body.
Red blood cells are produced through a series of complex and specific steps. They are made in the bone marrow (inner part of some bones that make most of the cells in the blood), and when all the proper steps in their maturation are complete, they are released into the blood stream. The hemoglobin molecule is the functional unit of the red blood cells and is a complex protein structure that is inside the red blood cells. Contrary to most cells in the human body, red blood cells do not have a nucleus (metabolic center of a cell).
Even though the red blood cells (or RBCs) are made within the bone marrow, many other factors are involved in their production. For example, iron is a very important component of the hemoglobin molecule; erythropoietin, a molecule secreted by the kidneys, promotes the formation of red blood cells in the bone marrow.
The following are some key points summarizing anemia and red blood cells:
- Having the correct number of red blood cells and prevention of anemia requires cooperation among the kidneys, the bone marrow, and nutrients within the body. If the kidneys or bone marrow are not functioning, or the body is poorly nourished, then normal red blood cell count and function may be difficult to maintain.
- Anemia is actually a sign of a disease process rather than a disease itself. It is usually classified as either chronic or acute. Chronic anemia occurs over a long period of time. Acute anemia occurs quickly. Determining whether anemia has been present for a long time or whether it is something new, assists doctors in finding the cause. This also helps predict how severe the symptoms of anemia may be. In chronic anemia, symptoms typically begin slowly and progress gradually; whereas in acute anemia symptoms can be abrupt and more distressing.
- Red blood cells live about 100 days, so the body is constantly trying to replace them. In adults, red blood cell production occurs in the bone marrow. Doctors try to determine if a low red blood cell count is caused by increased blood loss of red blood cells or from decreased production of them in the bone marrow. Knowing whether the number of white blood cells and/or platelets have changed also helps determine the cause of anemia.
- In the United States, 2% to 10% of people have anemia. Other countries have even higher rates of anemia. Young women are twice as likely to have anemia than young men because of regular menstrual bleeding. Anemia occurs in both young people and in old people, but anemia in older people is more likely to cause symptoms because they typically have additional medical problems.
In general, there are three major types of anemia, classified according to the size of the red blood cells:
- If the red blood cells are smaller than normal, this is called microcytic anemia. The major causes of this type are iron deficiency (low level iron) anemia and thalassemia (inherited disorders of hemoglobin).
- If the red blood cells size are normal in size (but low in number), this is called normocytic anemia, such as anemia that accompanies chronic disease or anemia related to kidney disease.
- If red blood cells are larger than normal, then it is called macrocytic anemia. Major causes of this type are pernicious anemia and anemia related to alcoholism.
Some patients with anemia have no symptoms.
Others with anemia may feel:
- fatigue easily,
- appear pale,
- develop palpitations (feeling of heart racing),
- become short of breath.
Additional symptoms may include:
- hair loss,
- malaise (general sense of feeling unwell),
- worsening of heart problems.
It is worth noting that if anemia is longstanding (chronic anemia), the body may adjust to low oxygen levels and the individual may not feel different unless the anemia becomes severe. On the other hand, if the anemia occurs rapidly (acute anemia), the patient may experience significant symptoms relatively quickly.
Any process that can disrupt the normal life span of a red blood cell may cause anemia. Normal life span of a red blood cell is typically around 120 days. Red blood cells are made in the bone marrow.
Anemia is caused essentially through two basic pathways.
Anemia is either caused:
- by a decrease in production of red blood cell or hemoglobin,
- by a loss or destruction of blood.
As more common classifications of anemia (low hemoglobin) is based on the MCV, or the volume of individual red blood cells.
- If the MCV is low (less than 80), the anemia is categorized asmicrocytic anemia (low cell volume).
- If the MCV is in the normal range (80-100), it is called a normocytic anemia (normal cell volume).
- If the MCV is high, then it is called a macrocytic anemia (large cell volume).
Looking at each of the components of a complete blood count (CBC), especially the MCV, a physician can gather clues as what may be the most common reason for anemia.
The treatment of the anemia varies greatly. First, the underlying cause of the anemia should be identified and corrected. For example, anemia as a result of blood loss from a stomach ulcer should begin with medications to heal the ulcer. Likewise, surgery is often necessary to remove a colon cancer that is causing chronic blood loss and anemia.
Sometimes iron supplements will also be needed to correct iron deficiency. In severe anemia, blood transfusions may be necessary. Vitamin B12 injections will be necessary for patients suffering from pernicious anemia or other causes of B12 deficiency.
In certain patients with bone marrow disease (or bone marrow damage from chemotherapy) or patients with kidney failure, epoetin alfa (Procrit, Epogen) may be used to stimulate bone marrow red blood cell production.
If a medication is thought to be the culprit, then it should be discontinued under the direction of the prescribing doctor.