Sickle Cell Disease: Causes, Symptoms, and Modern Treatment Options
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is sickle cell disease?
Sickle cell disease is a genetic blood disorder in which red blood cells become C-shaped and rigid, so they cannot flow easily through blood vessels. [1] The blockages limit oxygen delivery and cause intense pain, fatigue and possible organ damage. [1] It is managed with medicines, transfusions or bone marrow transplant, and gene therapies offer a potential cure for eligible patients.
Emergency warning
Go to the emergency room right away for severe pain that does not ease, fever, trouble breathing, chest pain, or signs of a stroke such as sudden weakness, trouble speaking, or confusion. [1] People with sickle cell disease can get seriously ill quickly.
What the research says
Hydroxyurea probably reduces pain episodes and other acute problems. A Cochrane review of 9 randomized trials (1,104 adults and children) found that hydroxyurea probably improves pain-related outcomes and life-threatening illness in people with HbSS or HbSβ⁰-thalassemia, with fewer episodes of acute chest syndrome and fewer blood transfusions. Evidence on long-term benefits and risks is still limited (Rankine-Mullings & Nevitt, Cochrane Database Syst Rev, 2022 [2]).
A one-time gene-editing therapy eliminated severe pain crises in almost all evaluable patients. In a phase 3 trial of exagamglogene autotemcel (exa-cel) in 44 patients aged 12 to 35 who had at least two severe crises a year, 29 of 30 evaluable patients (97%) were free of severe crises for at least 12 months in a row, and all 30 were free of hospital stays for crises. Safety matched the chemotherapy-like conditioning used before the infusion, and no cancers occurred over a median follow-up of 19.3 months (Frangoul et al., N Engl J Med, 2024 [3]).
What Is Sickle Cell Disease?
Sickle cell disease (SCD) refers to a group of inherited blood disorders caused by a variation in the HBB gene. [1] This change alters hemoglobin, the protein in red blood cells that carries oxygen around the body. [1] In SCD, the abnormal hemoglobin (hemoglobin S) makes red blood cells lose their flexible, donut-like shape and become stiff and crescent-shaped, like a farm tool called a sickle. [1]
Sickled cells do not move easily through small blood vessels and tend to stick together. [1] When they cluster, they block oxygen-rich blood from reaching tissues and organs. [1] This can cause sudden episodes of severe pain and a wide range of serious, sometimes life-threatening complications.
What are the genetics and types of sickle cell disease (SCD)?
SCD is inherited when a person receives two abnormal HBB genes, one from each parent. [1] It is often described as an autosomal recessive condition, but people with only one sickle gene (sickle cell trait) make both normal and sickled hemoglobin. [1] People with the trait usually have no symptoms but can pass the gene to their children. [1]
Several types of SCD exist, depending on the specific gene variations a person inherits. The most common and severe form is hemoglobin SS, often called sickle cell anemia. [1] Other forms, such as hemoglobin SC and sickle cell beta thalassemia, can cause different levels of symptoms.
Type of SCD | Genetic composition | Typical severity |
Hemoglobin SS (HbSS) | Two copies of the hemoglobin S gene | Most common and most severe form [1] |
Hemoglobin SC (HbSC) | One hemoglobin S gene and one hemoglobin C gene | Usually mild to moderate symptoms [1] |
HbS beta thalassemia | One hemoglobin S gene and one beta thalassemia gene | Varies with the amount of normal hemoglobin made |
Sickle cell trait | One hemoglobin S gene and one normal gene | Usually no symptoms (carrier) [1] |
What are the symptoms and early signs of sickle cell disease?
Symptoms usually begin when a baby is about five or six months old. [1] The hallmark of SCD is the sickle cell crisis (vaso-occlusive crisis): episodes of intense pain in the back, legs, arms, or chest that can last from a few hours to several weeks or longer. [1]
Other common problems include ongoing fatigue, paleness, and weakness, because sickled red blood cells have a shorter lifespan than healthy ones. [1] Jaundice (yellowing of the skin and the whites of the eyes) is also common. [1] In young children, painful swelling of the hands and feet, called dactylitis, is often one of the first visible signs.
What complications can sickle cell disease cause?
Reduced blood flow can damage many organs. Acute chest syndrome is a life-threatening lung complication, and blood clots such as deep vein thrombosis and pulmonary embolism are also possible. [1] Over time, a lack of steady oxygen supply can cause lasting damage to the heart, liver, and kidneys. [1]
Sickled cells can also block blood flow to the brain and cause a stroke, even in children (see our guide to pediatric stroke). The spleen, which helps fight infection, is often damaged, which raises the risk of infections such as pneumonia and meningitis. Vision loss, leg ulcers, and avascular necrosis (bone tissue death) can also occur. [1] During pregnancy, SCD increases the risk of preeclampsia, miscarriage, and low birth weight. [1]
Complication | What happens | Potential impact |
Sickle cell crisis | Blocked blood flow causes intense pain | Temporary or chronic disability |
Acute chest syndrome | Lung infection or trapped sickled cells | Life-threatening breathing problems |
Splenic sequestration | Blood becomes trapped in the spleen | Sudden, severe anemia |
Avascular necrosis | Bone tissue dies from poor blood supply | Joint pain and loss of mobility |
How is sickle cell disease diagnosed and screened?
In many places, including the United States, SCD screening is part of routine newborn testing. [1] It usually uses a simple heel-prick blood sample taken shortly after birth. [1] Early diagnosis matters because it lets care teams start preventive treatment, such as antibiotics, that lowers the risk of serious problems in early childhood.
Families with a known HBB gene variation can use prenatal testing. Chorionic villus sampling or amniocentesis can show whether a developing baby has inherited the disease or the trait, which helps parents plan care. [1]
How is sickle cell disease managed and treated?
Treatment aims to reduce the number of pain crises and prevent complications. Supportive care includes antibiotics to prevent infection, pain management, plenty of fluids, and regular blood transfusions for some people to raise the number of healthy red blood cells. [1] Medicines such as hydroxyurea make red blood cells less likely to sickle. [1] [2]
Treatments that aim to cure SCD are now available. A bone marrow (stem cell) transplant can potentially cure the disease by replacing the patient’s marrow with healthy donor cells, although finding a matched donor can be hard. [1] Gene therapies, which edit or modify a patient’s own cells so they make functional hemoglobin, offer new hope for people with severe disease. [1] [3]
Conclusion
Sickle cell disease is a complex, lifelong condition that needs steady medical care and a personal care plan. Pain crises and organ complications are serious, but treatment is changing quickly. With early diagnosis and access to modern therapies, many people with SCD can control their symptoms better and look ahead to improved health.
What are the next steps for sickle cell disease?
If you or your child has severe pain, trouble breathing, or extreme fatigue, get medical help right away. If you carry the sickle cell trait or have a family history, genetic counseling can help you understand your options before pregnancy.
Trusted resources: Cleveland Clinic: Sickle Cell Disease.
Frequently Asked Questions
What is sickle cell disease?
Sickle cell disease is a group of inherited blood disorders in which red blood cells become stiff and C-shaped and can block blood flow.
How do you get sickle cell disease?
Sickle cell disease is inherited when a child receives an abnormal HBB gene (such as the sickle gene) from each parent.
What is a sickle cell crisis?
A crisis is a painful episode that happens when sickled cells block blood flow to tissues and organs. It is also called a vaso-occlusive crisis.
Can adults develop sickle cell disease?
No. It is a genetic condition present from birth, although symptoms may not appear until a baby is about five or six months old.
What is the difference between sickle cell disease and sickle cell trait?
Sickle cell disease means having two abnormal HBB genes and usually causes symptoms. Sickle cell trait means having one sickle gene and one normal gene, and it usually causes no symptoms.
What are the most common symptoms?
Severe pain, fatigue, paleness, jaundice, and painful swelling of the hands and feet are common signs.
How is sickle cell disease diagnosed?
Most babies are diagnosed through newborn blood screening. Prenatal tests such as chorionic villus sampling or amniocentesis can also detect it before birth.
Is there a cure for sickle cell disease?
A bone marrow (stem cell) transplant can potentially cure the disease, and gene therapies are now available for eligible patients. Many people are managed with medicines and supportive care.
What triggers a pain crisis?
Triggers vary, but dehydration, infection, and low oxygen levels can contribute to sickling.
How does hydroxyurea help?
Hydroxyurea helps the body make more fetal hemoglobin, which makes red blood cells less likely to sickle.
Are there special risks during pregnancy?
Yes. Sickle cell disease raises the risk of preeclampsia, miscarriage, and low birth weight, so pregnancy needs specialist care.
What is dactylitis?
Dactylitis is painful swelling of the hands and feet, and it is often one of the first signs of sickle cell disease in babies.
Can sickle cell disease cause a stroke?
Yes. Sickled cells can block blood flow to the brain and cause a stroke, even in young children.
What is acute chest syndrome?
Acute chest syndrome is a serious lung complication with chest pain, fever, and trouble breathing that needs emergency care.
When should I go to the emergency room?
Seek emergency care for severe pain, fever, trouble breathing, or signs of a stroke.
Related Reading
Amniocentesis: Why It's Done, What Happens, Risks and What Your Results Mean explains the prenatal test that can detect this condition before birth.
References
Cleveland Clinic. Sickle Cell Disease. Cleveland Clinic. August 13, 2025. https://my.clevelandclinic.org/health/diseases/12100-sickle-cell-disease
Rankine-Mullings AE, Nevitt SJ. Hydroxyurea (hydroxycarbamide) for sickle cell disease. Cochrane Database Syst Rev. 2022;9(9):CD002202. PMID 36047926. https://doi.org/10.1002/14651858.CD002202.pub3
Frangoul H, Locatelli F, Sharma A, et al. Exagamglogene autotemcel for severe sickle cell disease. N Engl J Med. 2024;390(18):1649-1662. PMID 38661449. https://doi.org/10.1056/NEJMoa2309676
Medical Disclaimer
This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this article.
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