Sickle cell disease (SCD) is a genetic disorder that causes red blood cells to assume the shape of a sickle or the letter “C”. Hemoglobin levels, a protein that helps carry oxygen to red blood cells, are also usually low.
Red blood cells are usually round. When a person has SCD, abnormal hemoglobin types cause their red blood cells to change shape. This change makes it harder for red blood cells to move through the body and carry oxygen around the body. Reduced oxygen and blood flow to vital organs like the kidneys can cause pain and even life-threatening disease.
Low hemoglobin is common in people with SCD and can cause anemia. Sickle cell anemia is a form of SCD.
Read on to learn more about how sickle cell anemia can affect structure and hemoglobin levels, and how doctors can diagnose and treat this disease.
Hemoglobin levels in people with SCD are typically in the range of 6–11 grams per deciliter (g/dL), while in people without SCD it is around 12 mg/dL.
Lower hemoglobin levels can make it harder for red blood cells to carry oxygen around the body. This can lead to a variety of symptoms, including pain and fatigue. Over time SCD could affect most organs, including the eyes, kidneys, and liver.
In addition to causing low hemoglobin levels, SCD also alters hemoglobin, causing cells to sickle. These cells die early.
Sickle cells are also more likely to stick together, which can increase the risk of dangerous blood clots and pulmonary embolism.
Does sickle cell trait affect hemoglobin levels?
If a person has a sickle cell trait, it means they carry one gene for SCD, not two. Sickle cell disease is usually a benign condition that does not affect health or hemoglobin levels.
Because people with sickle cell anemia only have one gene that affects hemoglobin, they usually have enough normal hemoglobin to prevent them from developing symptoms.
Can physical activity affect hemoglobin levels?
When a person experiences intense physical stress — such as being at a high altitude, or when an untrained person is exercising at great intensity — some of their red blood cells can leach out.
As a result, a person can develop a life-threatening complication called rhabdomyolysis, which damages muscles, causing them to break down and release harmful substances into the blood.
In sickle cell anemia, the hemoglobin protein is abnormal. A genetic mutation within the HBB The gene causes the hemoglobin to contain a chemical called valine instead of glutamic acid in protein chains that make up hemoglobin. This damages the red blood cells, causing them to drain and die sooner than usual.
That HBB Gene is responsible for the formation of beta globin chains, which are a component of hemoglobin.
The premature death of red blood cells can mean that both hemoglobin and erythrocyte levels are chronically low. So, in addition to blood cells sticking together and transporting oxygen less effectively, a person does not have enough red blood cells to transport oxygen effectively.
Changes in hemoglobin structure
Hemoglobin is made up of four protein subunits: two subunits of alpha globin and two of beta globin.
In people with SCD, certain mutations within the HBB Gene can change the structure of hemoglobin. Specifically, mutations code for an abnormal version of beta-globin, or HbS. This can only occur in one of the two beta globin subunits.
However, in sickle cell anemia, both beta-globin subunits of hemoglobin are replaced by abnormal HbS. This distorts the red blood cells and causes them to assume a crescent shape.
In other types of SCD, the hemoglobin subunits can be replaced with other abnormal types of hemoglobin, such as HbC. These can also change the shape of red blood cells.
The type of SCD a person has affects the symptoms they experience. The genes a person inherits determine the type of SCD they develop.
The most common types of SCD are:
- Homozygous hemoglobin SS: This variant is the most common form of SCD and means that a person inherits two copies of the “S” sickle gene – one from each parent. This is the most severe manifestation of SCD. Doctors call it sickle cell anemia.
- Hemoglobin sickle cell anemia: People with this milder type of SCD inherit an “S” sickle gene and a “C” sickle gene, which is another type of abnormal hemoglobin gene.
- Hemoglobin sickle cell beta thalassemia: This version of SCD means a person gets an “S” sickle protein and a gene for beta thalassemia, which is another type of abnormal hemoglobin. There are two subtypes: beta0 thalassemia, a more severe form, and beta+ thalassemia, which tends to be milder.
people with access to medical care usually get a diagnosis as a newborn. Routine newborn screening in the United States uses a drop of blood to look for signs of hemoglobin abnormalities. This screening can help medical professionals diagnose SCD.
If a person has not had a newborn screening test or does not live in a country that offers this type of screening, they may have blood tests to detect SCD as an adult.
Some lab tests can separate the hemoglobin to look for the different variants and quantify them from blood samples. These tests include:
- Hemoglobin electrophoresis: This technique can identify the different types of hemoglobin.
- High Performance Liquid Chromatography: This technique also detects most types of hemoglobin.
- Isoelectric Focusing: This is a very sensitive detection method.
Although hematopoietic stem cell transplantation has potential as a cure for SCD they are not generally available. There is no cure available for most people, which means that treatment focuses primarily on treating the symptoms.
A doctor can recommend lifestyle management strategies to avoid some complications related to the condition. These strategies can include:
- Drink plenty of water
- wash your hands often to reduce this risk of infection
- avoid high altitudes
Pain-relieving drugs can help people with SCD manage pain episodes or pain crises. During a sickle cell crisis, a person may need to stay in the hospital. When red blood cell and hemoglobin counts become very low, a person may need a blood transfusion.
It is important for people with SCD to stay up to date on vaccinations and practice safe food handling, as they are at higher risk of serious complications if they contract an infection.
SCD can cause numerous complications and shorten a person’s life, especially if they do not have access to proper medical care. Possible complications are:
In sickle cell anemia, a person’s hemoglobin levels are chronically low. This can cause several complications. However, the severity of complications varies from person to person and is highly dependent on the type of SCD a person is suffering from.
It is important that all people with SCD receive quality medical care, maintain a healthy lifestyle, and know the signs of an emergency so they can seek help promptly if needed.