Anemia

The facts

Anemia is a condition where the number of healthy red blood cells (RBCs) in the blood is less than normal. RBCs transport oxygen throughout the body, so a shortage of these cells can be serious.

Iron-deficiency anemia is very common, affecting children and women of all ages - especially women who are menstruating. It's estimated that at least one-fifth of all women in North America suffer from iron-poor blood.

Sickle cell anemia is another well-known type of anemia. This condition affects several million people worldwide. People most commonly affected include those with ancestors from Africa, the Middle East, the Mediterranean regions, and India. It affects about 80,000 African-Americans in the US. Every year, 1 in 12 African-American babies are born with a genetic potential to pass sickle cell anemia on to their children. It's estimated that 1 birth out of 400 among African-Americans will produce a child with the disease.

Aplastic anemia is a rare but extremely serious disorder that results when the bone marrow fails to produce blood cells. It's estimated that there are 2 to 12 new cases per million population per year. It occurs in both adults and children.

Anemia of chronic disease is a mild form of anemia that is seen in people with diseases that last more than 1 to 2 months. Such diseases include tuberculosis, HIV, cancer, kidney disease, and liver disease.

Causes

Anemia is not an actual disease; it's a condition that's caused by some other problem. There are 3 basic ways you can develop anemia:

1) Blood loss. The most common cause of anemia in North America is menstruation. As many as 40% of women are borderline anemic, usually because their diet lacks the proper nutrients to replace their monthly blood loss. Another frequent cause is gastrointestinal (GI) bleeding due to illnesses like ulcerative colitis, diverticulitis, and colon cancer. Use of certain drugs such as acetylsalicylic acid (aspirin) and nonsteroidal anti-inflammatory drugs (NSAIDs) may also cause GI bleeding.

Other conditions that can cause bleeding include:

• hemophilia
• hemorrhoids
• hookworms

2) Low production of healthy red blood cells. Insufficient iron in the diet is the most common cause of anemia worldwide. Vitamin B₁₂ and folic acid tend to also be lacking. These deficiencies are less common in North America, but still do occur. People likely to have dietary iron-deficiency anemia are infants, pregnant women, and teenagers going through a growth spurt. Slow bleeding can also cause iron-deficiency anemia. Even healthy people lose up to 1 mL of blood a day in their stool. A slightly larger amount can easily go unnoticed and yet be enough to cause anemia.

The cause of anemia of chronic disease is not completely understood. It is related to a decreased production of red blood cells.

Individual red blood cells only last about 4 months and must be replaced by new ones, which are manufactured in the bone marrow. If the marrow is destroyed or so badly damaged that it can't produce enough RBCs, it's called aplastic anemia. Some drugs and radiation therapy can kill marrow, but the most common cause is an autoimmune reaction. That's when cells that normally protect you against disease attack your own tissue instead. In 75% of cases, the cause of the autoimmune reaction isn't known.

Other conditions that can destroy bone marrow and cause aplastic anemia include viral hepatitisand severe rheumatoid arthritis. Fanconi anemia is a rare inherited aplastic condition in which the bone marrow is deficient. Very occasionally, pregnancy can cause temporary aplastic anemia.

Anemia is common in people with severe kidney disease because the kidneys make a hormone called "erythropoietin," which causes the bone marrow to produce red blood cells as they are needed by the body. Diseased kidneys cannot produce enough of this hormone to keep the body supplied with red blood cells, leading to anemia.

3) Rapid destruction of red blood cells. Healthy bone marrow can only produce so many RBCs a month. If the body is destroying cells faster than they are made, anemia will result. Old, "worn out" RBCs are mostly broken down in the spleen, the organ that filters the blood and removes undesirable material. Some conditions can cause the spleen to grow larger. Liver disease or a blood clot obstructing blood as it leaves the spleen are 2 possible causes of hypersplenism (enlarged spleen), and malaria is another. An oversized spleen can trap and destroy even healthy RBCs, causing anemia.

Sickle cell anemia and thalassemia are fairly common inherited diseases in which the RBCs are deformed. Sickle cell is widespread among African-Americans, while thalassemia tends to run in families of Mediterranean descent. It is a genetic disease that occurs when individuals receive a copy of the sickle cell gene from both parents, resulting in grossly misshapen RBCs. The spleen recognizes them as abnormal, and it grows to cope with the extra workload of killing them. This causes anemia. Interestingly, the gene that causes sickle cell disease also imparts resistance to, or protection from, a parasite that causes malaria.

Anemia can also be caused by a combination of factors. Anemia is very common in people with cancer. In fact, about half of people with cancer develop anemia. It can have a variety of different causes, including chemotherapy or radiation therapy, which damage the bone marrow where red blood cells are produced; tumors in the bone marrow; blood loss; poor nutrition; or some combination of these reasons.

In people with severe kidney disease, anemia is caused by a combination of decreased production of red blood cells, decreased red blood cell lifespan, and blood loss related to dialysis.

Symptoms and complications

The symptoms of anemia vary, depending on the degree of RBC loss or shortage.

Menstrual bleeding or iron deficiency tends to cause a mild chronic anemia with symptoms of fatigue, pallor, and weakness.

If anemia is due to major blood loss, such as in cases of severe GI bleeding caused by ulcers, you may feel dizzy and very weak especially if you stand up suddenly.

Severe anemia can cause tissues and organs to be completely starved of blood and oxygen. When this happens, cells rapidly die in a process called ischemia.

In sickle cell anemia, which affects one in 400 African-Americans, RBCs, which are normally disc-shaped become sickle-shaped. This abnormal shape of the cells causes them to get lodged in small blood vessels, stopping normal blood flow. People with this disease may get serious ischemia in their feet, sometimes requiring amputation. People with sickle cell are at high risk of stroke, since the sickle-shaped cells can easily clot together, forming masses that block blood flow in the brain's blood vessels.

In patients with cancer, the most common symptoms of anemia are usually fatigue and shortness of breath. This makes it difficult for cancer patients to keep up their usual energy levels and activities, and can have very negative effects on their daily lives.

Making the diagnosis

Your doctor will ask for a blood sample that will be sent to the laboratory for a RBC count. This measures the number of red blood cells per liter of blood. Your blood will also be checked for levels of white blood cells (WBCs), platelets, and various other blood components. The laboratory will also look at the size and shape of your red blood cells. The different levels and how the blood cells look can tell the doctor a lot about what's causing the anemia. For instance, low red and white cells suggest a condition involving the bone marrow. The doctor will then test for other conditions, depending on the results of your initial blood test.

Treatment and prevention

The treatment for anemia depends on the underlying illness causing it. Severe bleeding can only be treated with blood transfusions. You also need regular transfusions of blood if you have a serious chronic type of anemia, for example Fanconi anemia or sickle cell anemia.

People who receive regular transfusions may eventually get overloaded with iron, which can damage organs and even lead to death. Bone marrow transplants could potentially remove the need for transfusions, but only if a suitable donor is found. This procedure can be difficult and dangerous; therefore, it's only considered in serious, potentially life-threatening cases of Fanconi anemia and other lethal aplastic anemias.

With new drugs for sickle cell anemia, the average life expectancy is now about 45 years (up from 14 years in 1975).

Iron supplements are used to treat iron-deficiency anemia. Infants who have this problem tend to be bottle-fed. A baby can absorb 6 times more iron from human milk than from cow's milk. You may want to take iron supplements for yourself when breast-feeding your child. Iron supplements will also help in cases of mild anemia that's due to GI or menstrual bleeding.

Vitamin B₁₂, vitamin C, and folic acid are all crucial to red blood cell production, therefore a deficiency in any one of these vitamins puts you at risk for anemia. Good sources of vitamin B₁₂ include beef and fish. Vegetables don't contain this vitamin, so if you don't eat meat, fish, or dairy products, you'll need to take vitamin B₁₂ supplements. Sources of folic acid include spinach and alfalfa sprouts.

When anemia is caused by decreased production of red blood cells, such as in cancer or severe kidney disease, a medication called epoetin alfa can be used. This medication mimicks the action of the natural hormone erythropoietin, which causes the bone marrow to produce more red blood cells.