Sickle Cell Anemia

Sickle cell anemia is an inherited blood disorder that arises from a single amino acid substitution in one of the component proteins of hemoglobin. The component protein, or globin, that contains the substitution is defective. Hemoglobin molecules constructed with such proteins have a tendency to stick to one another, forming strands of hemoglobin within the red blood cells. The cells that contain these strands become stiff and elongated—that is, sickle shaped.

Sickle-shaped cells—also called sickle cells—die much more rapidly than normal red blood cells, and the body cannot create replacements fast enough. Anemia develops due to the chronic shortage of red blood cells. Further complications arise because sickle cells do not fit well through small blood vessels, and can become trapped. The trapped sickle cells form blockages that prevent oxygenated blood from reaching associated tissues and organs. Considerable pain results in addition to damage to the tissues and organs. This damage can lead to serious complications, including stroke and an impaired immune system. Sickle cell anemia primarily affects people with African, Mediterranean, Middle Eastern, and Indian ancestry. In the United States, African Americans are particularly affected.

The energy demands of the bone marrow for red blood cell production compete with the demands of a growing body. Children with sickle cell anemia have delayed growth and reach puberty at a later age than normal. By early adulthood, they catch up on growth and attain normal height; however, weight typically remains below average.

Acute chest syndrome can occur at any age, and is caused by sickle cells blocking the small blood vessels of the lungs. This blockage is complicated by accompanying problems such as infection and pooling of blood in the lungs. Affected persons experience fever, cough, chest pain, and shortness of breath. Recurrent attacks can lead to permanent lung damage.

Early identification of sickle cell anemia can prevent many problems. The highest death rates occur during the first year of life due to infection, aplastic anemia, and acute chest syndrome. If anticipated, steps can be taken to avert these crises. With regard to long-term treatment, prevention of complications remains a main goal. Sickle cell anemia cannot be cured—other than through a risky bone marrow transplant—but treatments are available for symptoms.

Pain management

Pain is one of the primary symptoms of sickle cell anemia, and controlling it is an important concern. The methods necessary for pain control are based on individual factors. Some people can gain adequate pain control through over-the-counter oral painkillers (analgesics), local application of heat, and rest. Others need stronger methods, which can include administration of narcotics.

Blood transfusions

Blood transfusions are usually not given on a regular basis but are used to treat painful crises, severe anemia, and other emergencies. In some cases, such as treating spleen enlargement or preventing stroke from recurring, blood transfusions are given as a preventative measure. Regular blood transfusions have the potential to decrease formation of hemoglobin S, and reduce associated symptoms. However, regular blood transfusions introduce a set of complications, primarily iron loading, risk of infection, and sensitization to proteins in the transfused blood.

Drugs

Infants are typically started on a course of penicillin that extends from infancy to age six. This treatment is meant to ward off potentially fatal infections. Infections at any age are treated aggressively with antibiotics. Vaccines for common infections, such as pneumococcal pneumonia, are administered when possible.

Emphasis is being placed on developing drugs that treat sickle cell anemia directly. The most promising of these drugs is hydroxyurea, a drug that was originally designed for anticancer treatment. Hydroxyurea has been shown to reduce the frequency of painful crises and acute chest syndrome in adults, and to lessen the need for blood transfusions. Hydroxyurea seems to work by inducing a higher production of fetal hemoglobin. The major side effects of the drug include decreased production of platelets, red blood cells, and certain white blood cells. The effects of long-term hydroxyurea treatment are unknown.

Bone marrow transplantation

Bone marrow transplantation has been shown to cure sickle cell anemia in severely affected children. Indications for a bone marrow transplant are stroke, recurrent acute chest syndrome, and chronic unrelieved pain. Bone marrow transplants tend to be the most successful in children; adults have a higher rate of transplant rejection and other complications.

The procedure requires a healthy donor whose marrow proteins match those of the recipient. Typically, siblings have the greatest likelihood of having matched marrow. Given this restriction, fewer than 20% of sickle cell anemia individuals may be candidates. The percentage is reduced when factors such as general health and acceptable risk are considered. The procedure is risky for the recipient. There is approximately a 10% fatality rate associated with bone marrow transplants done for sickle cell anemia treatment. Survivors face potential long-term complications, such as chronic graft versus host disease (an immune-mediated attack by the donor marrow against the recipient's tissues), infertility, and development of some forms of cancer.

In general, treatment of sickle cell anemia relies on conventional medicine. However, alternative therapies may be useful in pain control. Relaxation, application of local warmth, and adequate hydration may supplement the conventional therapy. Further, maintaining good health through adequate nutrition, avoiding stresses and infection, and getting proper rest help prevent some complications.