Sickle cell disease (SCD) refers to a group of genetic conditions that affect the red blood cells (RBCs) by altering their shape. The abnormally shaped cells are unable to perform the function of healthy RBCs efficiently. As a result, a person may experience various symptoms and complications.
SCD describes a group of genetic RBC disorders that affects roughly
RBCs have the vital role of carrying oxygen throughout the body. If they cannot perform this role due to SCD, a person may experience various
In this article, we discuss the differences between sickle cells and healthy RBCs. We also explain how these differences affect the function of sickle cells.
Sickle cells are a type of
Many different types of hemoglobin exist. The most common type in healthy RBCs is hemoglobin A (HbA). This type of hemoglobin provides RBCs with a soft, round shape that allows them to pass easily through blood vessels and deliver oxygen effectively. On average, these healthy RBCs live for 120 days before the body replaces them with new ones.
A person with SCD instead makes a different type of hemoglobin, which is known as hemoglobin S (HbS). This type of hemoglobin causes RBCs to distort into a C-shape, or the shape of a sickle. Unlike healthy RBCs, sickle cells only live for 10–20 days.
The type of hemoglobin a person produces can alter the shape of their RBCs. The hemoglobin protein consists of smaller subunits, which contain two chains of alpha-globin and two chains of beta-globin. A person with SCD has a gene alteration in the HBB gene, which is present on
This alteration provides the body with instructions to produce HbS instead of HbA. This change replaces a single building block of protein, known as an amino acid, in beta-globin. Specifically, it replaces glutamic acid with valine. This single change causes the RBCs to have the characteristic sickle shape.
Healthy RBCs are round and flexible, which allows them to move easily through blood vessels and transport oxygen around the body. Due to their C-shape and rigidity, sickle cells have difficulty passing through blood vessels. As they break apart easily, clump together, and stick to the walls of blood vessels, they may block the flow of oxygen-rich blood.
This clumping of red blood cells and lack of oxygen to tissue can cause severe pain, infections, and damage to the body. Doctors refer to these severe instances of pain as a
- acute chest syndrome
- organ damage
In severe cases, SCD
Everyone inherits two sets of genes that code for the production of hemoglobin — one from each parent. This is similar to how people receive the genes that determine their hair and eye color. The exact type of SCD a person has depends on what combination of genes they inherit.
Statistics show that SCD genes are more common in people of African, South and Central American, Middle Eastern, Asian, Indian, and Mediterranean descent.
There are several types of SCD. The most common types
- HbSS or sickle cell anemia: A person with this condition has inherited two SCD genes that both code the production of HbS. This tends to be the most severe type of SCD.
- HbSC: HbSC occurs when a person inherits a gene that codes for hemoglobin S and a gene that codes for another type of hemoglobin, known as
hemoglobin C (HbC). This type of hemoglobin causes a similar change to HbS but changes the amino acids in a slightly different way, resulting in a milder form of the disease.
- Sickle cell beta-thalassemia: HbS beta-thalassemia occurs when a person inherits a gene that codes for HbS and a gene that codes for beta-thalassemia, which is another condition that affects hemoglobin.
- HbAS or sickle cell trait (SCT): A person with SCT has inherited only one gene for HbS, with the other gene coding for HbA. In most cases, a person with SCT does not show symptoms, but the HbS gene can pass to their children.
The treatment for SCD can involve a variety of approaches, including medications, procedures, and lifestyle changes.
- pain relievers
- hydroxyurea (Hydrea), which can help reduce the number of sickle cell crises by increasing the amount of
fetal hemoglobin (HbF), a type of hemoglobin that sickling does not affect
- crizanlizumab (Adakveo), which binds to a protein called P-selectin to prevent RBCs from sticking together
- voxelotor (Oxbryta), which tries to prevent RBCs from forming the sickle shape
Several procedures also aim to reduce the severity of SCD symptoms:
- Blood transfusions: This option
involvesa person receiving blood that contains healthy RBCs from a compatible donor.
- Stem cell transplants: This procedure has the potential to cure SCD by
replacingan individual’s cells with donor cells that are free of sickling.
- Gene therapy: This treatment is similar to stem cell transplants and also offers a potential cure for SCD. Rather than using a donor, doctors modify a person’s own stem cells to produce healthy RBCs.
A person with SCD may be more susceptible to dangerous complications from an infection. However, they can take steps to minimize this risk. These
- washing the hands frequently
- receiving vaccinations, including the flu vaccination
- avoiding handling reptiles such as turtles, snakes, and lizards, as they carry Salmonella
- excluding raw eggs and unpasteurized dairy products from the diet
- cooking meat thoroughly before eating it
Sickle cell disease refers to a group of genetic conditions that affect the type of hemoglobin a person’s body produces. Different types of hemoglobin affect both the shape and function of red blood cells. This can lead to a person experiencing a variety of symptoms and health complications.
Treatments are available to minimize the effects of sickle cell disease and encourage the production of healthy red blood cells.