SICKLE CELL DISEASE

By ¹Obiri Darko Stella, ²Sackey Lyanne, and ³Kwakye Sylvester.

Image from Forbes

Sickle cell disease or sickle cell anemia is a genetic disease of the red blood cells (RBCs). Normally, RBCs are shaped like discs, which gives them the flexibility to travel through even the smallest blood vessels. However, with this disease, the RBCs have an abnormal crescent shape resembling a sickle. This makes them sticky and rigid and prone to getting trapped in small vessels, which blocks blood from reaching different parts of the body.

Sickle cell disease is an autosomal recessive condition meaning an individual needs two copies of the sickle cell gene for the disease to develop.

Causes

Sickle cell is an inherited disease caused by a defect in a gene. A person will be born with sickle cell disease only if two genes are inherited — one from the mother and one from the father. A person who inherits just one gene is healthy and said to be a “carrier” of the disease. A carrier has an increased chance of having a child with sickle cell disease if he or she has a child with another carrier. For parents who are each carrier of a sickle cell gene, there is a 1 in 4 or a 25 % chance of having a child with sickle cell disease.

Risk Factors

Having a family history of sickle cell disease increases your risk for the disease. Sickle cell disease is more common in certain ethnic groups, including:

People of African descent, including African-Americans (among whom 1 in 12 carries a sickle cell gene)

Hispanic-Americans from Central and South America

People of Middle Eastern, Asian, Indian, and Mediterranean descent

Types

HbSS- People who have this form of sickle cell disease inherit two sickle cell genes (“S”), one from each parent. This is commonly called sickle cell anemia and is usually the most severe form of the disease.

HbSC- People who have this form of sickle cell disease inherit a sickle cell gene (“S”) from one parent and the other parent a gene for an abnormal hemoglobin called “C”. Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. This is usually a milder form of sickle cell disease.

HbS beta-thalassemia- People who have this form of sickle cell disease inherit one sickle cell gene (“S”) from one parent and one gene for beta-thalassemia, another type of anemia, from the other parent. There are two types of beta-thalassemia: “0” and “+”. Those with HbS beta 0-thalassemia usually have a severe form of sickle cell disease. People with HbS beta +-thalassemia tend to have a milder form of sickle cell disease.

There also are a few rare types of Sickle cell disease:

HbSD, HbSE, and HbSO- People who have these forms of sickle cell disease inherit one sickle cell gene (“S”) and one gene from an abnormal type of hemoglobin (“D”, “E”, or “O”). Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. The severity of these rarer types of sickle cell disease varies.

Symptoms and Complications

The following is a list of symptoms and complications associated with sickle cell disease. However, each person may experience symptoms differently. Symptoms and complications may include:

Anemia- Because sickled cells are short-lived or destroyed, there are fewer red blood cells available in the body. This results in anemia. Severe anemia can make you feel dizzy, short of breath, and tired.

Pain crisis, or sickle crisis- This occurs when the flow of blood is blocked to an area because the sickled cells have become stuck in the blood vessel. The pain can occur anywhere, but most often occurs in the chest, arms, and legs. Infants and young children may have painful swelling of the fingers and toes. Interruption in blood flow may also cause tissue death. Pain crisis, or sickle crisis. This occurs when the flow of blood is blocked to an area because the sickled cells have become stuck in the blood vessel. The pain can occur anywhere, but most often occurs in the chest, arms, and legs. Infants and young children may have painful swelling of the fingers and toes. Interruption in blood flow may also cause tissue death.

Acute chest syndrome- This occurs when sickling occurs in the chest. This can be life-threatening. It often occurs suddenly, when the body is under stress from infection, fever, or dehydration. The sickled cells stick together and block the flow of oxygen in the tiny vessels in the lungs. It resembles pneumonia and can include fever, pain, and a violent cough.

Splenic sequestration (pooling)- Crises are a result of sickle cells pooling in the spleen. This can cause a sudden drop in hemoglobin and can be life-threatening if not treated promptly. The spleen can also become enlarged and painful from the increase in blood volume. After repeated episodes, the spleen becomes scarred and permanently damaged. Most children, by age 8, do not have a working spleen either from surgical removal or from repeated episodes of splenic sequestration. The risk of infection is a major concern of children without a working spleen. Infection is the major cause of death in children younger than age 5 in this population.

Stroke- This is another sudden and severe complication of people with sickle cell disease. The misshapen cells can block the major blood vessels that supply the brain with oxygen. Any interruption in the flow of blood and oxygen to the brain can result in severe brain damage. If you have one stroke from sickle cell anemia, you are more likely to have a second and third stroke.

Jaundice- Jaundice is a common sign and symptom of sickle disease. Sickle cells do not live as long as normal red blood cells and, therefore, they are dying faster than the liver can filter them out. Bilirubin (which causes the yellow color) from these broken down cells builds up in the system causing jaundice.

Priapism- This is a painful obstruction of the blood vessels in the penis by sickle cells. If not promptly treated, it can result in impotence.

Diagnosis

Sickle cell disease is diagnosed with a simple blood test. It most often is found at birth during routine newborn screening tests at the hospital. In addition, sickle cell disease can be diagnosed before birth. Because children with sickle cell disease are at an increased risk of infection and other health problems, early diagnosis and treatment are important.

Treatment

Early diagnosis and prevention of complications are critical in sickle cell disease treatment. Treatment aims to prevent organ damage including strokes, prevent infection, and treat symptoms. Treatment may include:

Pain medications- This is for sickle cell crises.

Drinking plenty of water daily (8 to 10 glasses)- This is to prevent and treat pain crises. In some situations, intravenous fluids may be required.

Blood transfusions- These may help treat anemia and prevent stroke. They are also used to dilute the sickled hemoglobin with normal hemoglobin to treat chronic pain, acute chest syndrome, splenic sequestration, and other emergencies.

Vaccinations and antibiotics- These are used to prevent infections.

Folic acid- Folic acid will help prevent severe anemia.

Hydroxyurea- This medication helps reduce the frequency of pain crises and acute chest syndrome. It may also help decrease the need for blood transfusions. The long-term effects of the medication are unknown.

Regular eye exams- These are done to screen for retinopathy.

Bone marrow transplant- Bone marrow transplants can cure some people with sickle cell disease. The decision to have this procedure is based on the severity of the disease and the ability to find a suitable bone marrow donor. These decisions need to be discussed with your doctor and are only done at specialized medical centers.

References

Centers for Disease Control and Prevention

Healthline

John Hopkins Medicine

American Society of Hematology

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A Ghanaian research body that employs the scientific methodology of systematic inquiry to understand society, explain behavior and inform lifestyle.