HIV infection often causes anemia, a decrease in the number of circulating red blood cells. Blood is made up of a variety of different cells, including red blood cells (erythrocytes), white blood cells (leukocytes), and cells that help in clotting (platelets). Anemia results when there are too few red blood cells because they are being destroyed, are not maturing correctly, and/or are not being produced adequately in the bone marrow.
Red blood cells carry oxygen throughout the body. If people don’t have enough red blood cells, they begin to feel tired and breathless, and have difficulty concentrating. This can have a serious, negative effect on quality of life. Severe, untreated anemia may have complications such as heart failure and other organ damage.
Many people with HIV also have problems with their levels of white blood cells (leukocytes). Leukocytes are white blood cells that respond to and protect the body from infection. HIV can attack leukocytes. When the number of white blood cells decreases, a dangerous condition called leukopenia can develop, which makes the body more prone to infections.
The specific type of white blood cells that respond directly to infection are called neutrophils. A decrease in these cells is called neutropenia, and can also seriously impair the body's ability to fight off infection.
People with HIV often have problems with their levels of platelets, cells in the blood that help with clotting.
When the body slows its production of platelets, and/or when platelets are destroyed at a higher-than-normal rate, a condition called thrombocytopenia occurs. People with this condition bleed and bruise easily.
The drugs used to treat HIV may cause anemia and other blood disorders. The drugs used to treat HIV as well as the drugs used to combat other infections associated with HIV can cause anemia and other blood disorders. This is because these drugs can impair the production of leukocytes, red blood cells, and/or platelets in the bone marrow.
Treatment for anemia targets the underlying problem first, and the symptoms of anemia second.
There are a number of different kinds of anemia and other types of low blood counts, all caused by different problems. Serious anemia can be treated by transfusion or by using drugs that increase red blood cell production. Decreases in some other types of blood cells can be treated by using growth factors that stimulate production of the depleted cells. Initial evaluation should focus on identifying the underlying cause of the anemia such as infection, chronic disease, cancer, drugs, or HIV infection.
Anemia in AIDS patients is often caused in part, by bone marrow suppression, which is common in people with advanced HIV infection. Anemia is more common among people with advanced HIV infection, and signals a more rapid progression toward AIDS. In HIV, anemia of chronic disease (ACD) often occurs and results from the impairment of red cell production in the bone marrow. This impairment is due to the release of inhibitory substances (cytokines) and inappropriately low levels of the hormone erythropoietin. ACD can also occur in people who have other infections associated with HIV.
HIV infection itself seems to cause anemia. Late-stage HIV infection appears to have a negative effect on levels of erythropoietin, the hormone that drives the body to produce red blood cells. HIV infection may also have an effect on red blood cells, helping to decrease their lifespan in the blood and preventing the bone marrow from adequately replacing old and dying red blood cells. The HIV virus may infect early red blood cells in the marrow, altering their development.
Drug therapy can cause blood complications by suppressing the bone marrow. The following are a few of the drugs known to cause anemia, leukopenia, or neutropenia in HIV-infected people:
- Zidovudine (AZT or Retrovir)
- Ganciclovir (Cytovene)
- Trimethoprim-sulfamethoxazole (Bactrim; Septra)
- Alpha-interferon (Roferon-A; Intron A)
- Flucytosine (Ancobon)
- Amphotericin B (Fungizone)
- Pyrimethamine (Daraprim; Fansidar)
Infections associated with HIV or tumors in the marrow can cause anemia. In adults, the various cells that make up the blood are produced and mature in the bone marrow. Tumors or infections invading the marrow can disrupt this process by crowding out normal bone marrow cells. Furthermore, infections themselves can cause anemia without bone marrow invasion.
- Mycobacterium avium complex, which is in the same family as tuberculosis, is a rare infection except when it is associated with HIV. Infection probably happens after drinking or eating contaminated water or food. Once inside the body, the infection can spread to the blood, the organs, and the marrow.
- Histoplasmosis capsulatum and Pneumocystis carinii are both opportunistic infections. Both can invade the marrow and cause anemia.
- Cancers. Individuals with HIV are more prone to certain cancers, including Kaposi's sarcoma—a cancer that causes purple, brown, or red skin blotches—and non-Hodgkin's lymphoma, a cancer of the lymph system. These cancers can spread to the marrow and disrupt blood cell production.
- Parvovirus B19 can cause acute anemia by stopping red blood cells from developing. In this condition, called pure red blood cell aplasia, red blood cell precursors decline sharply.
As with anemia, thrombocytopenia (a decrease in the cells called platelets) and neutropenia (a decrease in white blood cells called neutrophils) are usually caused directly by HIV, by drugs, or by infection. Although anemia sometimes occurs alone, low blood counts tend to come in groups in HIV. Anemia and leukopenia, for example, tend to occur together; often in patients with advanced disease. Low levels of platelets (thrombocytopenia) may occur early in the course of the disease. HIV also appears capable of directly infecting the cells in the bone marrow that produce platelets. While uncommon, AIDS patients can develop platelet disorders called thrombotic microangiopathies. These occur when platelets rapidly start to clot in the body's small blood vessels. Red blood cells become trapped in the widespread clots, and platelets are used up. The outcome is anemia and thrombocytopenia, often associated with organ damage.
Examples of these disorders include thrombotic thrombocytopenia purpura (TTP) and hemolytic uremic syndrome (HUS). Both of these disorders are life-threatening, and require emergency treatment.
In AIDS patients, bleeding associated with infection or cancer of the digestive system may result in anemia. Widespread infections and tumors can invade the walls of the gastrointestinal tract, damaging blood vessels and allowing blood to escape into the digestive tract, resulting in anemia.
Some people with HIV, particularly children, have nutritional problems that lead to anemia.
- The body's iron stores can be lost through bleeding, as occurs sometimes with cancer or infection.
- Folate deficiency causes anemia. Folate, a necessary nutrient, allows the body to produce and maintain new cells. Absorption of dietary folate is impaired in HIV disease.
- Low levels of vitamin B12 also cause anemia. In HIV disease, diarrhea from medications or infections can prevent proper absorption of vitamin B12.
Pre-existing medical conditions or medical conditions resulting from HIV infection may lead to anemia or leukopenia.
- Liver disease resulting from hepatitis C infection can cause enlargement of the spleen (splenomegaly). One of the roles of the spleen is to remove aging blood cells from the body. When the spleen is enlarged, this process can be accelerated, causing anemia. Splenomegaly can also cause decreases in the number of platelets in the blood.
- Kidney disease is an important cause of anemia. The kidney produces erythropoietin, a substance that helps drive production and maturation of red blood cells. When the kidney is diseased, erythropoietin levels in the body are often diminished.
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