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What is Sickling?
Sickling is when the hemoglobin inside red blood cells sticks or clumps together, causing the cell to become fragile, rigid, and crescent—or sickle—shaped.

Sickling is when the hemoglobin inside red blood cells sticks or
clumps together, causing the cell to become fragile, rigid, and
crescent—or sickle—shaped. Take a closer look at how red blood cells
become distorted and how these sickled cells can affect your body.

What Causes Sickling?

Normal adult hemoglobin (HbA) looks and functions normally all the time. Hemoglobin sickle (HbS) molecules that are created due to having 2 copies of an abnormal HBB gene look and work normally in a high-oxygen state, such as while carrying oxygen to your cells and organs. However, when in a low-oxygen state, such as after delivering oxygen to your cells and organs, the HbS molecules can change shape. This change in shape, known as a conformational change, causes these HbS molecules to stick to one another. When there are many HbS molecules in a cell, these clumped together HbS molecules form long chains called polymers in a process called polymerization. These clumps (polymers) of HbS molecules distort the red blood cells, making them fragile and rigid as well as forming them into their characteristic sickled, or crescent, shape.

Normal adult hemoglobin (HbA) looks and functions normally all the time. Hemoglobin sickle (HbS) molecules that are created due to having 2 copies of an abnormal HBB gene look and work normally in a high-oxygen state, such as while carrying oxygen to your cells and organs. However, when in a low-oxygen state, such as after delivering oxygen to your cells and organs, the HbS molecules can change shape. This change in shape, known as a conformational change, causes these HbS molecules to stick to one another. When there are many HbS molecules in a cell, these clumped together HbS molecules form long chains called polymers in a process called polymerization. These clumps (polymers) of HbS molecules distort the red blood cells, making them fragile and rigid as well as forming them into their characteristic sickled, or crescent, shape.

The amount of HbS you have compared with other forms of hemoglobin in the cell determines how likely it is for the hemoglobin molecules to clump together (polymerize) and for your red blood cells to become sickled.

Consequences of Sickling

Sickled red blood cells are very rigid and sticky and can have difficulty moving through small blood vessels. They can slow or block blood flow in these blood vessels, preventing oxygen from properly circulating in the body as pictured in the image below. These sickled cells are also fragile and can break down prematurely, lasting only 10 to 20 days throughout the body, compared to 90 to 120 days for healthy red blood cells.

These blockages and broken down red blood cells cause damage to blood vessels and organs leading to the signs and symptoms associated with sickle cell, including vaso-occlusive crises, anemia, and other acute and chronic complications. Over time, these symptoms and complications can lead to progressive organ damage including organ failure and even death.

Image showing sickling within blood vessels

Image showing sickling within blood vessels

Work with your healthcare team to make sure you are receiving comprehensive care that includes careful monitoring and management of acute and chronic complications before your symptoms progress.

Photo of Rev. Jimmie, living with sickle cell
 

There’s not a day—not one single day—that I’m not in pain. And I’m 40, going on 41. So when people ask me how I’m doing, how do you expect me to be doing? I’m in pain.

There’s not a day—not one single day—that I’m not in pain. And I’m 40, going on 41. So when people ask me how I’m doing, how do you expect me to be doing? I’m in pain.

REV. JIMMIE
Living With Sickle Cell

What Can You Do?

Understanding what causes your symptoms can help you and your loved ones spark meaningful discussions about a comprehensive care plan with your healthcare team. Become and stay active in monitoring your health, because no one knows your body better than you do.
Every voice, no matter how big or small,
can spark a conversation and action to
help drive change for sickle cell.


Recognizing how sickle cell impacts your
life may help spark important
discussions with others.
How does sickle cell affect you?