SICKLE CELL DISEASE(SCD)

       Sickle-cell disease (SCD), or sickle-cell anaemia (SCA) or sometimesdrepanocytosis, is a hereditary blood disorder, characterized by an abnormality in the oxygen-carrying haemoglobin molecule in red blood cells. This leads to a propensity for the cells to assume an abnormal, rigid, sickle-like shape under certain circumstances. Sickle-cell disease is associated with a number of acute and chronic health problems, such as severe infections, attacks of severe pain ("sickle-cell crisis"), and stroke, and there is an increased risk of death. Sickle-cell disease occurs when a person inherits two abnormal copies of the haemoglobin gene, one from each parent. Several subtypes exist, depending on the exact mutation in each haemoglobin gene. A person with a single abnormal copy does not experience symptoms and is said to have sickle-cell trait.Sickle cell anemia (uh-NEE-me-uh) is the most common form of sickle cell disease (SCD). SCD is a serious disorder in which the body makes sickle-shaped red blood cells. “Sickle-shaped” means that the red blood cells are shaped like a crescent.Sickle cell anemia is one type of anemia. Anemia is a condition in which your blood has a lower than normal number of red blood cells. This condition also can occur if your red blood cells don't contain enough hemoglobin.

       

        Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain an iron-rich protein called hemoglobin (HEE-muh-glow-bin). This protein carries oxygen from the lungs to the rest of the body.

Sickle cells contain abnormal hemoglobin called sickle hemoglobin or hemoglobin S. Sickle hemoglobin causes the cells to develop a sickle, or crescent, shape.

Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain and organ damage. It can also raise the risk for infection.

How is sickle cell anemia inherited?

Sickle cell anemia is inherited as an autosomal (meaning that the gene is not linked to a sex chromosome) recessive condition. This means that the gene can be passed on from a parent carrying it to male and female children. In order for sickle cell anemia to occur, a sickle cell gene must be inherited from both the mother and the father, so that the child has two sickle cell genes.

Treatments and drugs

Bone marrow transplant offers the only potential cure for sickle cell anemia. But finding a donor is difficult and the procedure has serious risks associated with it, including death.

Medications

Medications used to treat sickle cell anemia include:

• Antibiotics. Children with sickle cell anemia may begin taking the antibiotic penicillin when they're about 2 months of age and continue taking it until they're at least 5 years old. Doing so helps prevent infections, such as pneumonia, which can be life-threatening to an infant or child with sickle cell anemia. Antibiotics may also help adults with sickle cell anemia fight certain infections.
• Pain-relieving medications. To relieve pain during a sickle crisis, your doctor may advise over-the-counter pain relievers and application of heat to the affected area. You may also need stronger prescription pain medication.
• Hydroxyurea (Droxia, Hydrea). When taken daily, hydroxyurea reduces the frequency of painful crises and may reduce the need for blood transfusions. Hydroxyurea seems to work by stimulating production of fetal hemoglobin — a type of hemoglobin found in newborns that helps prevent the formation of sickle cells. Hydroxyurea increases your risk of infections, and there is some concern that long-term use of this drug may cause tumors or leukemia in certain people. However, this hasn't yet been seen in studies of the drug.

  Assessing stroke risk

  Using a special ultrasound machine (transcranial), doctors can learn which children have a higher risk of stroke. This test can be used on children as young as 2 years, and those who are found to have a high risk of stroke are then treated with regular blood transfusions.

  Vaccinations to prevent infections

  Childhood vaccinations are important for preventing disease in all children. But, these vaccinations are even more important for children with sickle cell anemia, because infections can be severe in children with sickle cell anemia. Your doctor will make sure your child receives all of the recommended childhood vaccinations. Vaccinations, such as the pneumococcal vaccine and the annual flu shot, are also important for adults with sickle cell anemia.

  Blood transfusions

  In a red blood cell transfusion, red blood cells are removed from a supply of donated blood. These donated cells are then given intravenously to a person with sickle cell anemia.
  Blood transfusions increase the number of normal red blood cells in circulation, helping to relieve anemia. In children with sickle cell anemia at high risk of stroke, regular blood transfusions can decrease their risk of stroke.

  Supplemental oxygen

  Breathing supplemental oxygen through a breathing mask adds oxygen to your blood and helps you breathe easier. It may be helpful if you have acute chest syndrome or a sickle cell crisis.

  Stem cell transplant

  A stem cell transplant, also called a bone marrow transplant, involves replacing bone marrow affected by sickle cell anemia with healthy bone marrow from a donor. Because of the risks associated with a stem cell transplant, the procedure is recommended only for people who have significant symptoms and problems from sickle cell anemia.

  Treating complications

  Doctors treat most complications of sickle cell anemia as they occur. Treatment may include antibiotics, vitamins, blood transfusions, pain-relieving medicines, other medications and possibly surgery, such as to correct vision problems or to remove a damaged spleen.

  Experimental treatments

  Scientists are studying new treatments for sickle cell anemia, including:
  • Gene therapy. Because sickle cell anemia is caused by a defective gene, researchers are exploring whether inserting a normal gene into the bone marrow of people with sickle cell anemia will result in the production of normal hemoglobin. Scientists are also exploring the possibility of turning off the defective gene while reactivating another gene responsible for the production of fetal hemoglobin — a type of hemoglobin found in newborns that prevents sickle cells from forming. Potential treatments using gene therapy are still a long way off, however. No human trials using genes specifically for sickle cell have yet been done.
  • Nitric oxide. People with sickle cell anemia have low levels of nitric oxide in their blood. Nitric oxide is a gas that helps keep blood vessels open and reduces the stickiness of red blood cells. Treatment with nitric oxide may prevent sickle cells from clumping together. Studies on nitric oxide have had mixed results so far.
  • Drugs to boost fetal hemoglobin production. Researchers are studying various drugs to devise a way to boost the production of fetal hemoglobin. This is a type of hemoglobin that stops sickle cells from forming.
  • Statins. These medications, which are normally used to lower cholesterol, may also help reduce inflammation. In sickle cell anemia, statins may help blood flow better through blood vessels.