What Is Sickle Cell Disease? A Complete Guide for Patients, Families, and Advocates
Published: 25 Apr 2026
Sickle cell disease is one of the most common genetic disorders in the world. It affects approximately 8 million people globally and more than 100,000 people in the United States. It causes chronic pain, organ damage, life-threatening complications, and a significantly reduced quality of life for the people it affects.
It is also one of the most underfunded and under-researched conditions in medicine — a disparity that is inseparable from the fact that it disproportionately affects Black Americans and people of African, Middle Eastern, Mediterranean, and South Asian descent.
Understanding sickle cell disease — what it is, how it works, what treatments exist, and what still needs to change — is the foundation of effective advocacy and meaningful progress.
This guide is for patients, families, caregivers, advocates, and anyone who wants to understand sickle cell disease more deeply.
What Is Sickle Cell Disease?
Sickle cell disease is a group of inherited red blood cell disorders caused by a mutation in the gene that produces hemoglobin — the protein inside red blood cells that carries oxygen throughout the body.
In a person without sickle cell disease, red blood cells are round and flexible. They move easily through blood vessels, delivering oxygen efficiently to tissues and organs.
In a person with sickle cell disease, the mutated hemoglobin — called hemoglobin S — causes red blood cells to become rigid and crescent-shaped, like a sickle. These misshapen cells do not move smoothly through blood vessels. They can stick together, clump, and block blood flow — causing the signature symptom of sickle cell disease: a pain crisis.
Sickle cells also break down faster than healthy red blood cells, causing chronic anemia — a shortage of healthy red blood cells that carries its own set of complications.
How Is Sickle Cell Disease Inherited?
Sickle cell disease is inherited in an autosomal recessive pattern, meaning a person must inherit two copies of the mutated gene — one from each parent — to have the disease.
A person who inherits one copy of the mutated gene and one normal gene has what is called sickle cell trait. People with sickle cell trait typically do not have the disease, though they can pass the gene to their children.
When two people with sickle cell trait have children, each child has a 25% chance of having sickle cell disease, a 50% chance of having sickle cell trait, and a 25% chance of having neither.
Genetic counseling is an important resource for individuals and couples who have sickle cell trait and are planning families.
Types of Sickle Cell Disease
Sickle cell disease is not a single condition — it is a group of disorders defined by the specific combination of hemoglobin mutations a person inherits.
The most common and typically most severe form is hemoglobin SS disease, also called sickle cell anemia. A person with this type has inherited the sickle cell gene from both parents.
Other types include hemoglobin SC disease, hemoglobin SB+ thalassemia, and hemoglobin SB0 thalassemia, each involving a different combination of hemoglobin mutations with varying degrees of severity.
Symptoms of Sickle Cell Disease
The symptoms of sickle cell disease vary by individual and by disease type. The most well-known symptom is the vaso-occlusive crisis — commonly called a pain crisis — which occurs when sickled cells block blood flow in the small blood vessels. Pain crises can be mild or severe enough to require hospitalization, and their frequency and intensity vary considerably from person to person.
Other common symptoms and complications include:
Anemia
Because sickle cells break down rapidly, people with sickle cell disease often have chronically low red blood cell counts. Anemia causes fatigue, weakness, and shortness of breath.
Acute chest syndrome
A serious and potentially life-threatening complication in which sickled cells block blood flow in the lungs. It is one of the leading causes of death in sickle cell disease and requires immediate medical treatment.
Stroke
Sickled cells can block blood flow to the brain, causing stroke. Children with sickle cell disease are at particular risk. Regular monitoring with transcranial Doppler ultrasound and preventive treatment with regular blood transfusions have significantly reduced stroke rates.
Organ damage
Chronic reduction in blood flow and oxygen delivery can damage the spleen, kidneys, liver, heart, and eyes over time. The spleen is often permanently damaged in early childhood, increasing susceptibility to certain infections.
Infections
Spleen damage impairs the immune system’s ability to fight certain bacteria, making people with sickle cell disease particularly vulnerable to infections. Preventive antibiotics and vaccines are standard parts of care.
Delayed growth and puberty
Chronic anemia and frequent illness can affect growth and development in children.
Avascular necrosis
Reduced blood flow can cause bone tissue to die — most commonly in the hip and shoulder joints — leading to chronic pain and disability.
Leg ulcers
Chronic reduced circulation can cause painful, slow-healing ulcers on the lower legs.
Treatments for Sickle Cell Disease
Treatment for sickle cell disease has advanced significantly over the past two decades, though access to those treatments remains uneven.
Hydroxyurea
For many years, hydroxyurea was the primary disease-modifying treatment for sickle cell disease. It works by increasing the production of fetal hemoglobin, which does not sickle. Hydroxyurea has been shown to reduce pain crises, acute chest syndrome episodes, and hospitalizations. Despite its effectiveness, it remains underutilized, particularly in communities with limited access to specialty care.
Blood transfusions
Regular blood transfusions can dilute sickle cells with donor red blood cells, reducing the risk of stroke and managing severe anemia. Chronic transfusion therapy requires careful monitoring for iron overload.
Bone marrow and stem cell transplant
Allogeneic stem cell transplant — using donor stem cells — is currently the only curative option for sickle cell disease. However, it requires a matched donor, carries significant risks, and has historically been available only to a small subset of patients.
Gene therapy
Two gene therapies for sickle cell disease received FDA approval in December 2023 — marking a historic milestone for the sickle cell community. Casgevy, developed using CRISPR-Cas9 gene editing, and Lyfgenia, a lentiviral gene therapy, both offer the potential for functional cure. However, the cost of these therapies — estimated at $2 million to $3 million per patient — raises serious concerns about access and equity.
Pain management
Managing pain crises is a central part of sickle cell care and remains one of the most challenging aspects — both clinically and in terms of patient experience. Stigma around pain management in sickle cell disease, particularly in emergency settings, has been extensively documented and is a persistent advocacy priority.
The Equity Gap in Sickle Cell Disease
The underfunding of sickle cell disease research relative to other genetic disorders is well-documented and widely recognized as a product of racial inequity. For decades, research funding, clinical attention, and treatment development lagged far behind diseases affecting predominantly white populations with similar or smaller patient populations.
This equity gap has real consequences for patients. Access to specialist care is uneven. Hydroxyurea — an effective and inexpensive treatment — remains underutilized. Emergency department experiences for sickle cell patients are frequently marked by inadequate pain management and systemic bias. And the new gene therapies, while transformative in their potential, are priced in ways that make them inaccessible to most of the people who need them.
Addressing these gaps requires advocacy — at the clinical, institutional, policy, and funding levels. It requires patient advocacy organizations with the capacity and the partnerships to push for change with one voice as a collective. And it requires the kind of cross-sector collaboration that brings together advocates, clinicians, researchers, and industry in a shared effort.
The Role of Advocacy in Sickle Cell Disease
The sickle cell community has a strong and growing advocacy movement. Organizations at the national, state, and local levels are doing critical work — educating patients and families, working alongside and holding lawmakers accountable, pushing for better clinical standards, advocating for research funding, and building community.
What the movement needs now is the infrastructure to make that advocacy more coordinated, more connected to the clinical and research ecosystem, and more capable of translating community trust into research progress and policy change.
That is what Elevate Impact is building — starting with the sickle cell community because it is where the need is most urgent and where the opportunity for impact is most clear.
Frequently Asked Questions
Sickle cell disease is caused by a mutation in the HBB gene that produces hemoglobin. A person must inherit two copies of the mutated gene — one from each parent — to have the disease.
Sickle cell anemia (hemoglobin SS disease) is the most common and typically most severe form of sickle cell disease. Sickle cell disease is the broader term for a group of related disorders caused by different combinations of hemoglobin mutations.
Sickle cell disease affects people whose ancestors came from regions where malaria was or is endemic — sub-Saharan Africa, the Mediterranean, the Middle East, and parts of South Asia. In the United States, it disproportionately affects Black Americans. Approximately 1 in 365 Black Americans is born with sickle cell disease.
Bone marrow and stem cell transplant has been used as a curative option for some patients. As of December 2023, two gene therapies have received FDA approval that offer the potential for functional cure in a broader population — though access and cost remain significant barriers.
In the United States, newborn screening for sickle cell disease is mandated in all 50 states. It is typically identified at birth through a blood test. Prenatal diagnosis is also possible through amniocentesis or chorionic villus sampling.
A pain crisis, or vaso-occlusive crisis, occurs when sickle-shaped red blood cells block blood flow in small blood vessels. It can cause severe pain anywhere in the body and is the most common reason for hospitalization among people with sickle cell disease.
Connect with patient advocacy organizations in the sickle cell community. Advocate for research funding and equitable access to new treatments. Support policies that address the racial equity gaps in sickle cell care. And consider joining Elevate Impact’s platform to connect with the broader rare disease and advocacy ecosystem.
Sickle cell disease is a serious, complex, and profoundly under-resourced condition. The people it affects deserve better clinical care, more equitable access to new treatments, and a research ecosystem that prioritizes their needs.
Progress requires everyone — patients, families, advocates, clinicians, researchers, and industry — working together in a coordinated, structured, and equitable way.
That is the work Elevate Impact is committed to supporting.
