Sickle cell disease: What you need to know about SCD

Although sickle cell disease (SCD) is not as widespread in the Philippines compared to other populations, it is still worth knowing what this disease is all about, especially as we observe World Sickle Cell Day on June 19.

World Sickle Cell Day is an awareness holiday that aims to increase public knowledge and provide an understanding of SCD, and the challenges experienced by patients and their families and caregivers. 

According to the World Health Organization (WHO), approximately 5 percent of the world’s population carries trait genes for haemoglobin disorders, mainly, sickle-cell disease and thalassaemia.

So, what is sickle cell disease?

According to Johns Hopkins Medicine, SCD is an inherited blood disorder, meaning it is passed down from a parent’s genes. 

SCD causes the body to make abnormal hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen to all parts of your body. 

When you have SCD, your body’s tissues and organs don’t get enough oxygen.

Healthy red blood cells are round and move easily all over the body. With SCD, the red blood cells are hard and sticky. They are shaped like the letter C, like a farm tool called a sickle. 

Johns Hopkins Medicine further explains that these damaged red blood cells (sickle cells) clump together. They can’t move easily through the blood vessels. They get stuck in small blood vessels and block blood flow. This blockage stops the movement of healthy oxygen-rich blood. This blockage can cause pain. It can also damage major organs.

Sickle cells die sooner than healthy cells. Normally the spleen helps filter infections out of the blood. But sickle cells get stuck in this filter and die. Having fewer healthy red blood cells causes anemia. The sickle cells can also damage the spleen, which makes you at greater risk for infections.

Types of SCD

According to the US Centers for Disease Control and Prevention, there are several types of SCD. 

The specific type of SCD a person has depends on the genes they inherited from their parents. 

People with SCD inherit genes that contain instructions, or code, for abnormal hemoglobin.

Here are the most common types of SCD:

HbSS­­­­

People who have this form of SCD inherit two genes, one from each parent, that code for hemoglobin “S.” Hemoglobin S is an abnormal form of hemoglobin that causes the red cells to become rigid, and sickle shaped. This is commonly called sickle cell anemia and is usually the most severe form of the disease.

HbSC

People who have this form of SCD inherit a hemoglobin S gene from one parent and a gene for a different type of abnormal hemoglobin called “C” from the other parent. This is usually a milder form of SCD.

HbS beta thalassemia

People who have this form of SCD inherit a hemoglobin S gene from one parent and a gene for beta thalassemia, another type of hemoglobin abnormality, from the other parent. There are two types of beta thalassemia: “zero” (HbS beta0) and “plus” (HbS beta+). Those with HbS beta0-thalassemia usually have a severe form of SCD. People with HbS beta+-thalassemia tend to have a milder form of SCD.

What causes sickle cell disease?

Johns Hopkins Medicine says SCD is an inherited disease caused by a defect in a gene:

• You are born with SCD only if 2 genes are inherited—1 from each parent.
• If you have just 1 gene you are healthy, but you are a carrier of the disease. If 2 carriers have a child, there is a greater chance their child will have SCD.
• Parents who are each a carrier of a sickle cell gene have a 1 in 4 chance of having a child with SCD.

Who is at risk for sickle cell disease?

Having a family history of SCD increases your risk for the disease. SCD mainly affects people whose families came from Africa, Central America, South America, the Middle East, Asia, India, the Mediterranean, or Southern Europe. 

What are the symptoms of sickle cell disease?

Each person’s symptoms may vary. They may be mild or severe.

SCD symptoms may include:

• Anemia –  This symptom is the most common one. Having fewer red blood cells causes anemia. Severe anemia can make you feel dizzy, short of breath, and tired.
• Yellowing of the skin, eyes, and mouth (jaundice) –  This symptom is common. Sickle cells don’t live as long as normal red blood cells. They die faster than the liver can filter them out. The yellow color is caused by a substance (bilirubin) that is released when the red blood cells die.
• Pain crisis, or sickle crisis. When sickle cells move through small blood vessels, they can get stuck. They can block blood flow and cause pain. The sudden pain can occur anywhere. But it most often happens in the chest, arms, and legs. Blocked blood flow may also cause tissue death.
• Acute chest syndrome. This condition occurs when sickle cells stick together and block oxygen flow in the tiny vessels in the lungs. It can be life-threatening. It often happens suddenly when the body is under stress from infection, fever, or dehydration. Symptoms may seem like pneumonia. They can include fever, pain, and a violent cough.
• Splenic sequestration (pooling). The spleen becomes enlarged and painful when sickle cells get stuck there. Fewer red blood cells are able to move, causing a sudden drop in hemoglobin. It can be deadly if not treated at once.
• Stroke. A stroke is another sudden and severe problem that occurs with this disease. The sickle cells can block the major blood vessels that bring oxygen to the brain. Any interruption in the flow of blood and oxygen to the brain can cause severe brain damage. If you have a stroke from SCD, you are more likely to have a second and third stroke.
• Priapism. The sickle cells block the blood vessels in the penis, causing great pain. If not treated right away, it can cause erectile dysfunction.

The symptoms of SCD may look like other blood disorders or health problems. 

SCD treatment 

Treatment for SCD will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

Early diagnosis and preventing further problems is critical in treating SCD. Treatment goals include preventing organ damage (including strokes), preventing infection, and treating symptoms. 

SCD treatment may include:

• Pain medicines. These are used for sickle cell crises.
• Drinking plenty of water daily (8 to 10 glasses). Doing so can prevent and treat pain crises. In some cases, IV (intravenous) fluids may be needed.
• Blood transfusions. These may help treat anemia and prevent stroke. They are also used to dilute the sickled hemoglobin with normal hemoglobin. It is done to treat chronic pain, acute chest syndrome, splenic sequestration, and other emergencies.
• Red blood cell exchange.This process removes some abnormal red blood cells and replaces them with healthy red blood cells from a donor. This can help improve symptoms.
• Vaccines and antibiotics. These are used to prevent infections.
• Folic acid. This B vitamin helps prevent severe anemia.
• Hydroxyurea. This medicine helps reduce the frequency of pain crises and acute chest syndrome. It may also help decrease the need for blood transfusions.
• Voxelotor. This medicine is approved for people age 4 and older to reduce pain crises and improve anemia caused by red blood cell destruction.
• Crizanlizumab. This medicine is approved for people age 16 and older to reduce pain crises.
• L-glutamine. This medicine is approved for people age 5 and older to reduce pain crises.
• Regular eye exams. These are done to screen for an eye condition called retinopathy.
• Bone marrow transplant. A transplant can cure some people with SCD. The decision to have a transplant is based on the severity of the disease and finding a suitable donor. These decisions need to be discussed with your provider. Transplants are done only at specialized medical centers.
• Gene therapyNew gene therapies have been approved to treat SCD. Talk with your provider (or your child’s provider) about these treatments.