Sickle cell anemia–Causes-Symptoms-Diagnosis-Treatment–Prognosis

Other Names: - Sickle cell disease, Hemoglobin SS disease, Hemoglobin S disease, HbS disease, Sickle cell disorders, Sickling disorder due to hemoglobin S.

Sickle cell anemia (SCA) is a genetic blood disorder caused by the formation of distorted or "sickled" red blood cells. The sickling occurs due to the presence of abnormal hemoglobin.

Sickle cell anemia is one of the most prevalent inherited blood disorders mostly affecting Africans and African –Americans.

The geographical distribution of the SCA gene directly co- relates with malaria-prone areas throughout the world. Sickle cell anemia is very common in people who have their origins in Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.


It is estimated that in the United States, SCA affects 70,000–100,000 African Americans with the disease affecting 1 out of every 500 African American births. SCA also affects 1 out of every 36,000 Hispanic Americans at birth.

Normal RBCs are disc- or concave -shaped and closely resemble doughnuts minus the holes. They are manufactured in the spongy tissue of the bone marrow and have a life span of about 120 days. RBCs are made up of an iron- containing protein called hemoglobin (Hb), which imparts the color red to the blood and also helps in the transport of oxygen to body parts. They cruise through the blood vessels smoothly. However any change in its shape can cause problem with the flow dynamics.

Each RBC` contains approx. 280 million of hemoglobin molecules. Hemoglobin is composed of protein called globulin and a molecule called heme (which binds to iron) which is responsible for taking up oxygen and the release of carbon dioxide in the lungs. The primary function of RBCs is to carry the oxygen to the body tissues. On reaching the cells of the body the hemoglobin of RBC releases the oxygen in exchange for carbon dioxide.

In those with SCA, the hemoglobin sticks together and appears fibre-like, causing the RBCs to stiffen and become C- shaped, like a sickle. Symptoms and problems of sickle cell disease are due to the hemoglobin S (HbS) molecule. It is this form of hemoglobin that gives the abnormal shape to the RBC. Hemoglobin S (HbS) when it loses its oxygen becomes rigid and rod-like and changes the red blood cells into a sickle or crescent shape from the normal disc or concave shape.

These sickled RBCs are extremely fragile and therefore rupture easily (medically called hemolysis) leading to low red blood cell (RBC) count and anemia symptoms. Besides the sickle- celled RBC has a life span of only 10-20 days. The quick turn round time for new RBCs can only happen if the bone marrow can keep pace. As this fails to happen, it results in anemia.

The stiff, sickled RBCs clump together and tend to stick to the wall of the blood vessels. They are circulated with difficulty and can even cause blockage of blood vessels leading to infection, tissue and organ damage along with a great deal of pain.

In patients with SCA, sickling is further triggered by conditions such as low oxygen levels, increased acidity and low volume of the blood resulting from dehydration, injury or when anesthesia is administered.

Early diagnosis is necessary for effective management of the disease so much so that mandatory screening of new-born babies is carried out in many developed countries. Newer methods of treatment and better medications have made it possible for people with SCA to live up to their fourth decade and beyond.

It is not possible to cure SCA. Hence treatment is almost always focused on managing the disease and preventing crisis. One should aim at preventing dehydration, infection, stress and avoidance of strenuous exercise.

The current recommended treatment for prevention of SCA crisis is to use the drug Hydroxyurea. The National Institute of Health in its guidelines (2008) advocates the use of the drug Hydroxyurea as it reduces the frequency of painful sickle cell crises and episodes of acute chest syndrome. The recommendation concludes that "the risks of serious side effects appear to be lower than previously thought, and that the risks of untreated sickle cell disease outweigh those of the drug".