Sickle Cell Anaemia

What Is Sickle Cell Anemia?

Sickle Cell Anaemia 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.

Normal red blood cells are disc-shaped and look like doughnuts without holes in the centre. They move easily through the blood vessels. Red blood cells contain an iron-rich protein called haemoglobin. This protein carries oxygen from the lungs to the rest of the body.

Sickle cells contain abnormal haemoglobin 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.

What Causes Sickle Cell Anemia?

When both parents have a normal gene and an abnormal gene, each child has a 25 percent chance of inheriting two normal genes; a 50 percent chance of inheriting one normal gene and one abnormal gene; and a 25 percent chance of inheriting two abnormal genes.

People who inherit a sickle hemoglobin gene from one parent and a normal gene from the other parent have sickle cell trait. Their bodies make both sickle hemoglobin and normal hemoglobin.

People who have sickle cell trait usually have few, if any, symptoms and lead normal lives. However, some people may have medical complications.

People who inherit both sickle hemoglobin genes from both parents, develop Sickle Cell Disease. Their bodies make mostly sickle hemoglobin and normal haemoglobin also to a lesser percentage.

People who have sickle cell trait can pass the sickle hemoglobin gene to their children.

Who Is at Risk for Sickle Cell Anemia?

Sickle cell anemia is most common in people whose families come from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.

What are the Signs & Symptoms?

The signs and symptoms of sickle cell anemia vary. Some people have mild symptoms. Others have very severe symptoms and often are hospitalized for treatment.

Sickle cell anemia is present at birth, but many infants don't show any signs until after 4 months of age.

The most common signs and symptoms are linked to anemia and pain. Other signs and symptoms are linked to the disease's complications. There are few signs called crisis, the patient usually presents with:
  • Severe pain in arms, back, abdomen and legs
  • fever
  • Strokes- one- sided weakness or paralysis in arms, face or legs; or finding difficulty in talking, walking and seeing. This is often the first and foremost sign of SCD.
  • Shortness of breath or difficulty in breathing
  • Chest pain
  • Severe infections
  • Blood flow blockage in liver or spleen
  • Anemia
  • Delayed growth
  • Hand & foot syndrome i.e. swelling in the feet and hands
  • Pale skin
  • Vision problems
  • Kidney failure
  • Pulmonary Hypertension

How Is Sickle Cell Anemia Diagnosed?

  • Complete Blood Count and PERIPHERAL Blood Smear: The characteristic finding of SCD is circulating sickle shaped red cells. Routine examination of the blood gives the diagnosis.
  • Reticulocytosis i.e. increase in young red blood cells is almost always seen.
  • Hemoglobin Electrophoresis: This is the cornerstone of diagnosis and is used to detect Hemoglobin S. HbA2 and often HbF are increased in patient with sickle cell-B thalassemia. Despite high level of HbF at birth, electrophoresis can detect HbS in the newborn.
  • Prenatal diagnosis may also be detected by examining the DNA from the chorionic villus biopsy or from the cells of amniocentesis.

How Is Sickle Cell Anemia Treated?

  • Folic acid
  • Penicillin prophylaxis
  • Pneumococcal vaccine.
  • All the infections should be identified and should be treated early.
  • Treatment of painful crisis or other complications.
Specific Treatment
  • Hydroxyurea: Datas have shown that it decreases the painful crisis episodes. This drug decreases Neutrophil concentration in the blood. Neutrophils play a key role in fostering Sickle cell crisis.
  • Red cell Transfusion: Used frequently in Sickle Cell Disease to increase Hb concentration and decrease the concentration of Sickle cells in the blood. It prevents the episodes of stroke in patients who have developed stroke or likely to develop one.
  • Exchange red cell transfusions: This is done to reduce the concentration of sickle cells without increasing the concentration of red cells during acute episodes of crisis.

Blood and Marrow Transplant (BMT) for Sickle Cell Disease

ALLOGENEIC BMT was first carried out in 1980 in a patient with Acute Leukemia who also had Sickle Cell Disease. Subseuqently, multicentric studies on BMT in Sickle Cell Disease has taken place in USA, France and Belgium.

This shows that 90% of the most severely affected patients with Sickle Cell Disease are cured with BMT from Matched Family Donors.

However, very few patients with Sickle Cell Disease have a Matched Family Donor. The Unrelated Donor Registries rarely offer a full matched donor for these patients.

BMT in Sickle Cell Disease has produced the best results one can expect in any severe inherited disorder. Despite such encouraging results, BMT in Sickle Cell Disease had hit a roadblock due to lack of suitably matched donors.

Recent studies have shown that Haploidentical BMT can cure the majority of patients with Sickle Cell Disease without any severe complication.

How is Conditioning for BMT done in Sickle Cell Disease?

Primarily Reduced Intensity conditioning is used in adults and conventional high dose chemotherapy in children.

Who can be a donor for BMT?

Although we prefer a matched family donor, a Half matched (Haploidentical) family donor or an unrelated cord blood are suitable alternatives. The result of cord blood transplantation has not been very encouraging.