Things That Can Go Wrong With Blood
Most of the time, blood functions without problems, but sometimes, blood disorders or diseases can cause illness. Diseases of the blood that commonly affect kids can involve any or all of the three types of blood cells. Other types of blood diseases affect the proteins and chemicals in the plasma that are responsible for clotting.
Diseases of the Red Blood Cells
The most common condition affecting RBCs is anemia, a lower-than-normal number of red cells in the blood. Anemia is accompanied by a decrease in the amount of hemoglobin. The symptoms of anemia — such as pale skin, weakness, a fast heart rate, and poor growth in infants and children — happen because of the blood's reduced capacity for carrying oxygen.
Anemia typically is caused by either inadequate RBC production or unusually rapid RBC destruction. In severe cases of chronic anemia, or when a large amount of blood is lost, someone may need a transfusion of RBCs or whole blood.
Anemia resulting from inadequate RBC production. Conditions that can cause a reduced production of red blood cells include:
- Iron deficiency anemia. The most common type of anemia, it affects kids and teens of any age who have a diet low in iron or who've lost a lot of RBCs (and the iron they contain) through bleeding. Premature babies, infants with poor nutrition, menstruating teenage girls, and those with ongoing blood loss due to illnesses such as inflammatory bowel disease are especially likely to have iron deficiency anemia.
- Lead poisoning. When lead enters the body, most of it goes into RBCs where it can interfere with the production of hemoglobin. This can result in anemia. Lead poisoning can also affect — and sometimes permanently damage — other body tissues, including the brain and nervous system. Although lead poisoning is much less common now, it still is a problem in many larger cities, especially where young children might ingest paint chips or the dust that comes from lead-containing paints peeling off the walls in older buildings.
- Anemia due to chronic disease. Kids with chronic diseases (such as cancer or human immunodeficiency virus infection) often develop anemia as a complication of their illness.
- Anemia due to kidney disease. The kidneys produce erythropoietin, a hormone that stimulates production of red cells in the bone marrow. Kidney disease can interfere with the production of this hormone.
Anemia resulting from unusually rapid red blood cell destruction. When RBCs are destroyed more quickly than normal by disease (a process called hemolysis), the bone marrow will make up for it by increasing production of new red cells to take their place. But if RBCs are destroyed faster than they can be replaced, a person will develop anemia.
Several causes of increased red blood cell destruction can affect kids:
- G6PD deficiency. G6PD is an enzyme that helps to protect red blood cells from the destructive effects of certain chemicals found in foods and medications. When the enzyme is deficient, these chemicals can cause red cells to hemolyze, or burst. G6PD deficiency is a common hereditary disease among people of African, Mediterranean, and Southeast Asian descent.
- Hereditary spherocytosis is an inherited condition in which RBCs are misshapen (like tiny spheres, instead of disks) and especially fragile because of a genetic problem with a protein in the structure of the red blood cell. This fragility causes the cells to be easily destroyed.
- Autoimmune hemolytic anemia. Sometimes — because of disease or for no known reason — the body's immune system mistakenly attacks and destroys RBCs.
- Sickle cell anemia, most common in people of African descent, is a hereditary disease that results in the production of abnormal hemoglobin. The RBCs become sickle shaped, they cannot carry oxygen adequately, and they are easily destroyed. The sickle-shaped blood cells also tend to abnormally stick together, causing obstruction of blood vessels. This blockage in the blood vessels can seriously damage organs and cause bouts of severe pain.
Diseases of the White Blood Cells
- Neutropenia occurs when there aren't enough of a certain type of white blood cell to protect the body against bacterial infections. People who take certain chemotherapy drugs to treat cancer may develop neutropenia.
- Human immunodeficiency virus (HIV) is a virus that attacks certain types of WBCs (lymphocytes) that work to fight infection. Infection with the virus can result in AIDS (acquired immunodeficiency syndrome), leaving the body prone to infections and certain other diseases. Newborns can become infected with the virus from their infected mothers while in the uterus, during birth, or from breastfeeding, although HIV infection of the fetus and newborn is usually preventable with proper medical treatment of the mother during pregnancy and delivery. Teens and adults can get HIV from sex with an infected person or from sharing contaminated needles used for injecting drugs or tattoo ink.
- Leukemias are cancers of the cells that produce WBCs. These cancers include acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphocytic leukemia (ALL), and chronic lymphocytic leukemia (CLL). The most common types of leukemia affecting kids are ALL and AML. In the past 25 years, scientists have made great advances in treating several types of childhood leukemia, most notably certain types of ALL.
Diseases of Platelets
- Thrombocytopenia, or a lower than normal number of platelets, is usually diagnosed because a person has abnormal bruising or bleeding. Thrombocytopenia can happen when someone takes certain drugs or develops infections or leukemia or when the body uses up too many platelets. Idiopathic thrombocytopenic purpura (ITP) is a condition in which the immune system attacks and destroys platelets.
Diseases of the Clotting System
The body's clotting system depends on platelets as well as many clotting factors and other blood components. If a hereditary defect affects any of these components, a person can have a bleeding disorder.
Common bleeding disorders include:
- Hemophilia, an inherited condition that almost exclusively affects boys, involves a lack of particular clotting factors in the blood. People with severe hemophilia are at risk for excessive bleeding and bruising after dental work, surgery, and trauma. They may experience episodes of life-threatening internal bleeding, even if they haven't been injured.
- Von Willebrand disease, the most common hereditary bleeding disorder, also involves a clotting-factor deficiency. It affects both males and females.
Other causes of clotting problems include chronic liver disease (clotting factors are produced in the liver) and vitamin K deficiency (the vitamin is necessary for the production of certain clotting factors).