Sickle cell anemia

Anemia is a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron. The red blood cells carry oxygen throughout the body. Sickle cell anemia is a specific type of anemia in which the hemoglobin is defective, causing the red blood cells to become shaped like a sickle or crescent. This abnormal shape interferes with the transportation of oxygen to the tissues.


Causes/associated factors
Genes are the basic unit of heredity. Every child inherits one gene for hemoglobin from each parent. If both genes are defective, the child will develop sickle cell anemia. The lifelong condition is usually diagnosed at about age 6 months. If a child inherits only one defective gene, he or she won't have the disease but will carry the sickle cell trait.
Those with the sickle cell trait usually have no symptoms, but they're able to pass the defective gene on to their children. Parents may not know they're carriers unless there's a family history of sickle cell anemia.

Sickle cell anemia is most common among people of African descent and ethnic groups originating from the Mediterranean, Cuba, Saudi Arabia, India, South America and Central America.

When the red blood cell is sickle-shaped, it can't effectively deliver oxygen to your tissues. Instead, it begins to stack up and block oxygen delivery. This process causes a periodic episode called sickle cell crisis, which can cause severe pain and low-grade fevers for hours or days. The crisis can develop spontaneously or in response to an infection or dehydration. These bouts of pain and fever can cause life-threatening organ damage, especially to the heart and liver. Any organ or tissue can be affected, however, such as the kidneys, bones and eyes. Some people rarely have a sickle cell crisis and live a nearly normal life. Others may have repeated episodes that require hospitalization.

In addition to a cycle of flare-ups and remissions (times when symptoms aren't present), sickle cell anemia is characterized by painful syndromes, such as hand-foot syndrome. With this condition, which develops in infancy, the small blood vessels in the hands or feet become blocked, causing pain, swelling and fever. A syndrome of chest pain caused by infection or trapped sickle cells in the lung may occur as well.

Eye problems often develop because the retina doesn't get enough oxygen. In severe cases, this can lead to blindness. An enlarged spleen is also possible. Normally, the spleen filters the blood. In children who have sickle cell disease, the spleen may become enlarged from the trapped red blood cells, which impairs its function. By adulthood, the spleen often shrinks due to flares and consequent scarring. When the spleen can't function as it should, severe infections can more easily develop.

Infections are a common problem for both children and adults who have sickle cell anemia. Some may be life threatening. Fortunately, with good health care, those who have sickle cell anemia can now expect to live productive lives well into adulthood.


Signs/symptoms
Depending on which organs or tissues are affected, symptoms may include:
shortness of breath
rapid heartbeat
fatigue
jaundice (yellowing of the skin and whites of the eyes)
bouts of pain and fever
frequent infections
nerve impairment
delayed growth and development, including delayed sexual maturation
skin sores, especially on the legs
visual problems
paleness
in infants, swelling of hands and feet

Diagnosis
Diagnosis is based on many factors, including your medical history, current symptoms and a physical exam. In most states, a specific blood test called hemoglobin electrophoresis is routinely done at birth. This test evaluates for the presence of abnormal hemoglobin.
Your doctor may use tests such as a bone scan, chest X-ray or CAT scan to determine if any complications from sickle cell anemia have occurred.


Treatment
The severity of sickle cell anemia varies considerably. It's a complicated condition that's best treated by an experienced doctor. A specialized sickle cell clinic in a major medical center is usually a good source of care.
Sickle cell pain can be severe and unpredictable, often beginning in childhood. Your doctor may recommend nonsteroidal anti-inflammatory medications (NSAIDs) and acetaminophen to help ease mild to moderate pain. Warm compresses may be recommended to soothe painful areas. Your doctor may prescribe oral narcotics (taken by mouth) for severe pain unless you're vomiting or can't take oral medication. In this case, injectable narcotics may be prescribed. Intravenous fluids may be needed for hydration, and supplemental oxygen is sometimes also required. Finally, your doctor may prescribe a daily supplement to meet your increased need for folic acid, which is used to make new red blood cells.

Blood tests to measure hemoglobin, white blood cells and platelets will be done routinely. Blood transfusions may be needed during sickle cell crises or even on a routine basis to help prevent complications. Blood transfusions can help correct the anemia by increasing the number of normal red blood cells in circulation. They may also help to prevent strokes in children and treat spleen enlargement before it becomes life threatening.

A cytotoxic medication called hydroxyurea is known for its use with cancer treatment, but may also be recommended if you have frequent, severe sickle cell crises. Hydroxyurea has been reported to relieve symptoms, decrease the need for blood transfusions and reduce the incidence of certain life-threatening complications. Because the medication has only recently been used as standard treatment for sickle cell anemia, its long-term side effects are still being studied. Most health professionals believe that the benefits far outweigh the risks, however.

Any infections will be treated early and aggressively with antibiotics. Antibiotics may also be given in the hopes of preventing infections. Penicillin is often given daily starting at age 2 months until age 5. This regimen is helpful in preventing a life-threatening pneumonia that often occurs in young children who have sickle cell anemia. Because of the increased susceptibility to infections in general, yearly flu shots and routine Haemophilus influenza type b (Hib) and pneumococcal vaccinations are recommended.

Surgery is sometimes used depending on the situation, but medical management is generally preferred. For example, gallstones, skin ulcers or painful joints may all require surgery. Laser surgery to correct or prevent vision problems may also be used in certain cases. For young patients, bone marrow transplantation may be considered when sickle cell anemia causes severe disease. Unfortunately, less than 20 percent of people who have sickle cell anemia have a sibling with matching bone marrow. Umbilical cord blood transplants may also be an option.

Other treatments currently being tested include the medications butyrate, clotrimazole and magnesium. Gene therapy has been successful in curing mice of sickle cell disease, and research continues in this area.


Complications
Complications of sickle cell anemia can affect various organs and tissues. For example, the condition may lead to:
stroke (a condition caused by a blood clot that blocks blood flow to part of the brain)
kidney, liver or heart failure
in the womb, decreased fetal blood flow
priapism (prolonged, painful penile erection)
infections, usually involving bone, lung, kidney or brain tissue
acute chest syndrome (a potentially life-threatening condition in which sickle cells become trapped in the lungs
gallstones
painful skin ulcers
painful joints
retinopathy (any disorder of the retina, the light-sensitive tissue found at the back of the eye that sends nerve impulses to the brain), including retinal detachment (a separation of the retina from the back of the eye; if left untreated, retinal detachment can cause loss of vision or blindness)

Pregnancy-specific information
If you have sickle cell anemia or carry the sickle trait, consider genetic counseling before planning a pregnancy. Simply having the trait may not complicate your pregnancy, but the abnormality could be passed on to your baby.
Pregnant women who have sickle cell anemia have a higher risk of sickle cell crises, miscarriages, preeclampsia (a serious condition that develops usually after the 20th week of pregnancy and disappears once the baby is born), preterm labor, and low birthweight babies. During your pregnancy, be sure to work with a doctor who's experienced in treating women with this condition. Folic acid supplements are usually prescribed. You may be given periodic blood transfusions throughout the pregnancy and antibiotics after delivery. Aggressive medical treatment may minimize the severity of anemia and the risk of sickle cell crises, which would be beneficial for both you and your baby.


Senior-specific information
Sickle cell anemia is considered a rare condition among older adults because the life expectancy of a person who has sickle cell anemia doesn't typically exceed age 50. With improved treatment, however, survival has improved dramatically over the last few decades. The prognosis may improve when gene therapy for the treatment of sickle cell disease becomes more advanced.

Prevention
Sickle cell anemia is an inherited condition. As such, prevention can begin with a basic understanding of genetics. Both parents must pass on an abnormal recessive gene for the child to develop sickle cell disease. If the child receives one normal gene and one abnormal gene, the normal gene is dominant and the child won't develop the condition. Parents who don't have sickle cell disease but do have the recessive gene that can be passed on to their children are called carriers. When both parents are carriers, their children have a 25 percent risk of developing sickle cell disease and a 50 percent risk of becoming carriers. If one parent has sickle cell anemia and the other is a carrier of the recessive gene, their children have a 50 percent risk of developing the disease or becoming carriers. If one parent has the disease and the other parent isn't a carrier of the recessive gene, their biological children have no risk. They'll all be recessive gene carriers, however, and could pass the gene on to their own biological children.
If you have sickle cell anemia, wear a medical identification tag, make sure your immunizations are current and consult your doctor at the first sign of an infection. Drink plenty of fluids, but avoid alcohol. They can lead to dehydration. It's also helpful to avoid precipitating factors whenever possible. Infection, dehydration and decreased oxygen (in high altitudes, for example) can trigger a sickle cell crisis. Other triggers may include anesthesia, strenuous exercise, stress, pregnancy, fatigue, smoking or exposure to cold.

It's important for babies in high-risk groups to be screened early, preferably before they leave the hospital. Children who have the condition should be monitored in a pediatric program designed to treat sickle cell anemia.