Characteristics/Symptoms

Sickle cell disease is an inherited blood disorder that affects red blood cells. Sickle cell patients have red blood cells that contain an abnormal type of hemoglobin called hemoglobin S. These red blood cells become sickle shaped (shaped like a "C") and experience difficulty passing through blood vessels. The sickle cells form clumps that stick to the blood vessels, the clumps block the blood flow that leads to important organs in the body. Episodes of pain/crises are the outcome of the blocked blood flow. Because of these complications, patients are expected to have a reduced life span of 30 years. Doctors can identify the disease at birth with a blood test. If not screened at birth, a blood sample can be used for a test called hemoglobin electrophoresis. This test can determine if you have the disease or if you are a carrier of the defected hemoglobin gene.

Genetic Cause

Sickle cell disease is an autosomal recessive genetic disorder. The hemoglobin “S” gene is found in the Region 15.5 on the short arm of the chromosome 11. The presence of two faulty genes is necessary for sickle cell anemia. If each parent carries one sickle hemoglobin gene and one normal gene, each child has a 25% chance of inheriting the disease, a 25% of not inheriting it, and a 50% chance of being an unaffected carrier.

Statistics

Sickle cell anemia is one of the most common genetic diseases in the country. More than 70,000 people in the US have the disease and more than 2 million people in the US carry the gene. African Americans are most commonly affected though. 1 In 12 African Americans carry the sickle cell trait. The explanation for this is that the disease originated in at least 4 places in Africa and in the Indian/Saudi Arabian subcontinent. 25% of West and Central Africans carry the sickle cell trait. And in Nigeria, 45,000 to 90,000 babies are born with sickle cell disease each year… The transatlantic slave trade was mainly responsible for introducing sickle cell disease to America. However, it had already spread to Southern Europe by the time of the slave trade. But sickle cell disease is now present in Portuguese, Spaniards, French Corsicans, Sardinians, Sicilians, mainland Italians, Greeks, Turks and Cypriots. And found in most of the Near and Middle East Countries like Lebanon, Israel, Saudi Arabia, Kuwait and Yemen, India and Sri Lanka. As you can see, Sickle cell disease is not only a health problem for the US but international as well.

Recent Discoveries

The understanding of sickle cell anemia has definitely bettered and changed over the last 10 years. Just in 1998, The Food & Drug Administration approved the drug, Droxia, for reducing episodes in adults with severe cases of sickle cell. Although it is not a cure for the disorder, it has helped with controlling the pain that comes with the sickle cell symptoms.
Early identification of sickle cell disease through screening as a newborn, early initiation of penicillin therapy, close medical monitoring, and early intervention to relieve the symptoms of painful episodes (all somewhat recent discoveries) has lead to life expectancy improving for sickle cell disease!

Identification/Diagnosis

Early diagnosis of sickle cell disease is extremely critical so children can receive proper treatment. Sickle cell is usually suggested when the abnormal sickle shaped cells in the blood are found under a microscope. Testing is usually done on a smear of blood using a low-oxygen preparation (sickle prep) Hemoglobin electrophoresis is the most commonly used diagnosis test. Hemoglobin electrophoresis tests, specifically, identifies the hemoglobin in the blood by using electrical charges they have on their protein surfaces to separate them. With these tests, if the results show that the sickle hemoglobin is present, then a second test is performed to confirm the diagnosis. These blood tests tell if the patient carries the trait or not.

Fetal Diagnosis

Sickle cell can be identified while the mother is still pregnant. This is called, fetal diagnosis. Fetal diagnosis is possible for about 90% of pregnancies. But it is stressed that a previous homozygous normal or affected child or, otherwise, the couple's parents are necessary to confirm the linkage of variant genes to respective DNA markers. And if the appropriate markers are identified and their linkage to the sickle cell genes is verified, then the diagnosis can be performed at 16-18 weeks.

At first, fetal diagnosis was performed on a small amount of fetal blood from the placenta, umbilical cord, or fetal heart, either blindly, with ultrasound guidance, or through a fetoscope at the 20th week of pregnancy. But this fetal blood procedure was associated with 1-2% fetal loss and during the mid-trimester diagnosis of the affected fetus frequently led to a painful abortion. But the introduction of DNA techniques have took this procedure’s place. These techniques permit precise fetal diagnosis in the first trimester and termination of pregnancy.

The use of amniotic cells is the easiest way to DNA analysis. It provides results after the 17th week of pregnancy. The technique uses the aspiration of amniotic fluid with a long needle which is painless and safe. About 20 ml of fluid contains enough amniotic cells for removal of up to 20ug of DNA to identify the defect. The risk of fetal loss is lower than 0.5%.

Treatment/Therapies

Sickle cell health maintenance starts with early diagnosis preferably in the newborn period and includes vaccination against phneumoccus bacteria, penicillin prophylaxis and folic acid supple mentation. Treatment for complications, like the crises that come along with sickle cell, include antibiotics, pain management, intravenous fluids, blood transfusion, and surgery all backed up by psychosocial support. A drug, Hydroxyurea, is prescribed for the frequency of severe pain. And the drug mentioned in Topic 4, Droxia, which is a prescription form of Hydroxyurea is available for adult patients with sickle cell anemia. And blood transfusions can help reducing recurring pain crises, risk of stroke and other complications.

Future Prospects

The fact that there is no cure for sickle cell disease and because of how common it is, there’s a lot of research being done on the disorder. Just in 2008, researchers identified a gene that directly affects the production of a certain form of hemoglobin that is modifying the brutality of inherited blood disorders like sickle cell disease… This discovery could lead to new therapies for sickle cell that could eliminate the fetal complications of sickle cell like severe pain, damage to organs, infections and stroke. With all the research being done and recent discoveries being found, there is hope for sickle cell patients to look to.