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What Is Sickle Cell Disease?

Sickle cell disease (SCD) is a genetic blood disorder that affects how oxygen moves through the body.

In healthy blood, red blood cells are round and flexible. They travel smoothly through blood vessels and deliver oxygen to tissues and organs. In SCD, red blood cells become stiff and curved — shaped like a crescent or “sickle.” These cells do not move easily and can block blood flow.

When blood flow is blocked, oxygen cannot reach parts of the body that need it. This leads to pain and can damage organs over time.

What Is Sickle Cell Disease Caused By?

The Genetic Mutation Behind SCD

Sickle cell disease is caused by a change (mutation) in the hemoglobin gene. Hemoglobin is the protein inside red blood cells that carries oxygen. The mutation makes hemoglobin form hard fibers inside the red blood cell. This changes the cell’s shape from round to sickle-shaped.

How Sickle Cell Trait Is Passed From Parents to Children

A person develops sickle cell disease only when they inherit two sickle cell genes — one from each parent.

If a person inherits only one gene, they have sickle cell trait. They usually do not have symptoms but can pass the gene to their children.

When both parents carry the trait, each pregnancy has:

  • 1 in 4 chance the child has SCD
  • 1 in 2 chance the child has trait
  • 1 in 4 chance the child has neither

What Happens in the Body to Cause Sickle Cell Disease Symptoms?

How Red Blood Cells Change Shape

The abnormal hemoglobin causes red blood cells to become rigid and sticky. Instead of moving freely, they clump together.

Why Blood Flow Gets Blocked

These misshapen cells can get stuck in small blood vessels, slowing or stopping circulation.

What Happens When Blood Vessels are Blocked

Blocked blood vessels keep oxygen from reaching organs, causing pain and infections.

What is a Pain Crisis

Blocked blood vessels trigger something called a “pain crisis.” This is when people with sickle cell disease experience episodes of severe pain that can last hours, days, or even weeks and often require medical care.

Pain is commonly felt in:

  • Chest
  • Abdomen
  • Joints
  • Bones

How Sickle Cell Disease Affects the Body

Pain Episodes and Daily Life

Pain crises are unpredictable and can interrupt school, work, sleep, and daily routines.

Risk of Stroke and Acute Chest Syndrome

These misshapen cells can get stuck in small blood vessels, slowing or stopping circulation.

What Happens When Blood Vessels are Blocked

Blocked blood flow can affect the brain and lungs, leading to stroke or acute chest syndrome, both medical emergencies.

Organ Damage and Anemia

Sickle cells die faster than normal cells, causing anemia (a shortage of red blood cells). Over time, repeated blockages can damage organs such as the heart, kidneys, and spleen.

Living With Sickle Cell Disease

Why Specialized Care Is Important

SCD is a complex condition that requires coordinated medical care from providers experienced in treating it.

Managing Symptoms and Preventing Complications

Regular care helps reduce crises, detect complications early, and improve quality of life.

Treatments and Hope for the Future

Medications and Transfusion Therapy

Today’s treatments can help reduce painful episodes and help the body get the oxygen it needs. Blood transfusions may also prevent complications.

Gene Therapy and Emerging Treatments

New advances, like gene-based therapies and specialized care programs, are helping people with sickle cell disease live longer and healthier lives.
Understanding how sickle cell disease works in the body helps patients and families make informed decisions — and brings us closer to safer, more effective treatments for every Sickle Cell Warrior.