Sickle cell disease (SCD) is a group of inherited blood disorders that affect hemoglobin, the protein in red blood cells that carries oxygen. Some red blood cells can become rigid and sickle-shaped, which can block blood flow and cause pain and other serious health complications.
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Learn more about sickle cell disease from the CDC. This information is educational and does not replace medical advice.
SC WRLD / UNITE • EDUCATE • EMPOWER • REPRESENT
UNDERSTANDING SICKLE CELL
Sickle cell disease (SCD) is a group of inherited blood disorders affecting hemoglobin, the protein in red blood cells that carries oxygen. Sickle cell anemia (HbSS) is a form of SCD in which a person inherits a hemoglobin S gene from each parent. Other forms include HbSC and HbS beta-thalassemia. SCD is present from birth and is not contagious.
Normal blood cells vs. sickle blood cells
Normal red blood cells
Round, flexible discs that travel through small blood vessels to deliver oxygen.
Sickle-shaped red blood cells
Abnormal hemoglobin can make cells rigid, sticky, and crescent-shaped. They can break down early or block blood flow.
Original educational illustrations; these are not microscope photographs. Actual cells can vary in appearance.
Symptoms and complications
Symptoms vary and can include episodes of severe pain, fatigue from anemia, swelling of hands and feet, jaundice, and infections. Serious complications include acute chest syndrome, stroke, and organ damage.
Why it happens
Sickled red blood cells can break down faster than the body replaces them, causing anemia. Their shape and stiffness can also obstruct blood flow, causing pain and tissue damage.
Inheritance and sickle cell trait
SCD is inherited through hemoglobin genes. People with sickle cell trait generally have one hemoglobin S gene and one usual hemoglobin A gene. They usually do not have SCD but can pass the gene to their children. If both parents have sickle cell trait, each pregnancy has a 25% chance of HbSS, a 50% chance of trait, and a 25% chance of neither. Other gene combinations can produce other forms of SCD. Newborn screening and blood tests can identify SCD or trait.
Care and treatment
Care is individualized and may include regular specialist visits, vaccinations and infection prevention, pain management, hydroxyurea, and blood transfusions. Stem cell transplantation and gene therapies may be options for some people. Discuss the benefits and risks of treatment with a qualified sickle cell care team.
Seek urgent medical care for fever, chest pain, difficulty breathing, stroke-like symptoms, or other severe or unusual symptoms.
SC WRLD / KNOW THE SIGNS
SICKLE CELL CRISIS
What is a pain crisis?
A sickle cell pain crisis, also called a vaso-occlusive episode (VOE), occurs when sickled red blood cells obstruct blood flow and reduce oxygen delivery to tissues. It can begin suddenly, range from mild to severe, and last for hours or longer. Pain may affect the back, chest, abdomen, arms, legs, hands, or feet. Some people also live with chronic pain between episodes.
What can trigger a crisis?
Dehydration, infections or other illnesses, extreme heat or cold, sudden temperature changes, high altitude or low oxygen, and physical or emotional stress may contribute to an episode. Sometimes there is no identifiable trigger. A crisis is not the person's fault.
Signs and symptoms
Sudden or worsening pain can feel sharp, stabbing, throbbing, or deep and may affect several areas at once. Swelling, fatigue, or other symptoms may accompany pain. Pain severity and location differ between people and between episodes.
During a pain crisis
Follow the individualized pain action plan provided by your sickle cell care team. If your clinician has advised it, rest, drink fluids as appropriate, use gentle warmth rather than extreme heat, and take prescribed pain medicines exactly as directed. Contact your care team or seek urgent care when pain is severe, unusual, worsening, or not controlled by your plan. Do not delay emergency care to try home remedies.
When to seek emergency help
Get emergency medical care right away for chest pain, coughing with fever or difficulty breathing; sudden weakness, facial droop, trouble speaking or seeing, or confusion; severe or unusual pain; fainting or signs of severe anemia; or sudden painful swelling of the abdomen, especially in a child. Fever of 101.3°F (38.5°C) or higher in someone with sickle cell disease needs immediate medical evaluation because infection can become serious quickly. Call 911 for stroke symptoms or severe breathing problems.
Chest pain, fever, cough, and breathing difficulty may signal acute chest syndrome, a life-threatening complication requiring hospital treatment.
SC WRLD / TYPES OF SICKLE CELL CRISIS
DIFFERENT TYPES OF CRISIS
“Sickle cell crisis” can refer to several different acute complications. Not every crisis is a pain episode, and some emergencies can occur with little or no pain. Symptoms may overlap, so a healthcare professional must determine the cause.
01 / Vaso-occlusive pain crisis
What happens: sickled cells and inflammation obstruct blood flow, causing tissue injury and pain. Pain may occur in the back, chest, abdomen, arms, or legs, and may last hours or days.
What to watch for: sudden or worsening pain, sometimes with swelling. Follow your individualized pain plan and seek medical care for severe, unusual, or uncontrolled pain. Chest pain with fever or breathing symptoms needs emergency evaluation for acute chest syndrome.
02 / Aplastic crisis
What happens: the bone marrow temporarily stops producing enough new red blood cells, often after parvovirus B19 infection. Because red blood cells already have a shorter lifespan in SCD, hemoglobin can drop rapidly.
What to watch for: unusual tiredness, marked paleness, dizziness, fast heartbeat, or shortness of breath. This needs urgent medical evaluation and may require a blood transfusion.
03 / Splenic sequestration crisis
What happens: blood suddenly pools in the spleen, which can enlarge rapidly and cause a dangerous fall in circulating blood volume and hemoglobin. It is particularly important in infants and young children, though it can occur in older people with some forms of SCD.
What to watch for: sudden left-sided abdominal swelling or pain, unusual paleness, weakness, rapid heartbeat, or faintness. This is a medical emergency. Families may be taught how to check spleen size by their care team.
04 / Hemolytic crisis
What happens: red blood cells break down faster than usual, causing a sudden worsening of anemia. This may be triggered by an infection or, rarely, occur in association with a transfusion reaction. Clinicians distinguish this from the ongoing hemolysis common in SCD.
What to watch for: increased jaundice, dark urine, marked fatigue, paleness, or shortness of breath. Seek prompt medical assessment, especially if symptoms occur after a transfusion.
05 / Acute chest syndrome
What happens: a new lung injury in SCD can develop during or after a pain crisis, sometimes associated with infection or blocked blood flow in the lungs. It can rapidly reduce oxygen levels.
What to watch for: chest pain, fever, cough, fast breathing, or difficulty breathing. Seek emergency care immediately. Acute chest syndrome is a serious complication, not simply an ordinary pain crisis.
06 / Stroke or neurologic emergency
What happens: disrupted blood flow to the brain can cause a stroke. This is another serious acute complication of SCD, rather than a separate pain-crisis subtype.
What to watch for: sudden facial droop, one-sided weakness or numbness, trouble speaking, new vision problems, severe unusual headache, or seizure. Call 911 immediately.
Important: when a crisis needs emergency care
Seek emergency care for fever of 101.3°F (38.5°C) or higher, chest pain, difficulty breathing, stroke symptoms, sudden abdominal swelling, fainting, or severe or unusual pain. Call 911 for stroke symptoms, severe breathing difficulty, or collapse. Do not assume every new symptom is a routine pain crisis.
Care and treatment differ by complication. A medical team may use pain medication, antibiotics, oxygen, carefully managed fluids, or blood transfusion when indicated. Always follow your personal sickle cell care plan.
Believe people when they describe their pain. Ask what practical support they need, respect their personal care plan, and help them access medical care without judgment. A person can be in severe pain even when they look well.
