Chapter 11 The Blood 343 Copyright Goodheart-Willcox Co., Inc. Hemophilia Hemophilia is a disorder in which the blood does not clot properly because one of the clotting factors responsible for coagulation is missing. There are 13 clotting factors involved in the coagulation process. As discussed earlier in this chapter, platelets and clotting factors form a blood clot to stop an injured blood vessel from bleeding. People with hemophilia typically lack either clotting factor VIII or IX. Hemophilia is usually inherited but, in very rare cases, may be acquired if the body forms antibodies that attack one of the clotting factors. Cases of hemophilia can range from mild to severe depending on which clotting factor is missing. This disease is more common in males, and it occurs in one out of every 5,000 births each year. Treatments include blood transfusions, transfusions of the deficient clotting factors themselves, or administration of drugs that increase the lacking clotting factors. Polycythemia Polycythemia, also known as polycythemia primary or polycythemia vera, is a condition in which the bone marrow manufactures too many red blood cells. Living at a high altitude contributes to polycythemia because long-term exposure to high altitude causes the kidneys to produce more erythropoietin. Erythro- poietin stimulates stem cell production in the bone marrow, and more erythropoietin leads to increased RBC production. However, people who live at a high altitude do not develop polycythemia unless they also have a rare genetic mutation that increases bone In the case of iron poisoning, the chelating drug binds with the iron and prepares it for elimination from the body via the urine. The drug is usually administered at night and is infused slowly over an eight-hour period, four to six nights a week. SELF CHECK 1. What are the three main causes of anemia? 2. Which type of anemia is the most common worldwide? 3. Which type of anemia is caused by the inability of the intestines to absorb vitamin B12? 4. Why might a person with rheumatoid arthritis be more likely to develop anemia than someone without rheumatoid arthritis? Other Common Blood Disorders and Diseases Anemia is not the only disorder that affects the blood. Many other diseases, disorders, and conditions are possible as well. Jaundice Jaundice is a condition that is actually a symptom caused by several disorders. Characterized by yellowing of the skin and whites of the eyes, it can be caused by an excess of bilirubin—a by-product of RBC breakdown—in the bloodstream. Bilirubin is typically converted to bile in the liver, so jaundice can result either from liver damage or from disease. Jaundice may also occur in newborns as the result of an immature liver. In addition, a newborn is more likely to be jaundiced when his or her Rh antigen is different from the mother’s. For example, if the mother is Rh-negative and the baby is Rh-positive, the mother’s antibodies may attack the baby’s red blood cells and release excess bilirubin, causing jaundice. This severe form of jaundice is not the usual cause of mild jaundice in newborns. Mild forms of infant jaundice are treated with phototherapy using ultraviolet light, which lowers the bilirubin levels in the baby’s blood (Figure 11.18). Infant jaundice is usually resolved within two to four weeks of birth. phakimata/iStock.com Figure 11.18 Phototherapy employs ultraviolet light to help break down excess bilirubin so that it can be excreted in the urine and feces.