Sickle cell disease is an inherited blood disorder in which red blood cells contain an abnormal hemoglobin that makes them stiff, sticky, and crescent-shaped. Those misshapen cells break down early and block small blood vessels, which causes anemia, episodes of severe pain, and damage to organs over time. It is lifelong, but with early diagnosis and good care most people now live well into adulthood.
In my practice, I meet families at every stage, from a newborn screening result to an adult managing decades of the condition. This guide walks through what the disease is, how it shows up, how it is diagnosed, and how it is treated. If you want a quick summary to share with relatives, our page of comprehensive facts about sickle cell disease is a good companion.
What Is Sickle Cell Disease?
Sickle cell disease is a group of inherited red blood cell disorders caused by a variant hemoglobin called hemoglobin S (HbS). Hemoglobin is the protein inside red cells that carries oxygen from the lungs to the tissues.
Healthy red cells are round, flexible discs that squeeze easily through the narrowest capillaries. When hemoglobin S gives up its oxygen, the molecules stick together into long rods called polymers. These rods bend the cell into a sickle shape and make it rigid.
Sickled cells cause trouble in two ways. They clog small vessels, cutting off blood flow to tissues, and they are destroyed quickly. A normal red cell lives about 120 days, while a sickle cell typically survives only 10 to 20 days, which is why chronic anemia is almost universal.
The condition affects people with ancestry from sub-Saharan Africa, the Mediterranean, the Middle East, India, and parts of Central and South America. In the United States it occurs in roughly 1 in 365 African American births. Patients often ask how that compares worldwide, which we cover in our article on whether sickle cell disease is rare.
Types of Sickle Cell Disease
“Sickle cell disease” is an umbrella term. The specific type depends on which two beta-globin genes a person inherits, and it strongly influences how severe the illness tends to be.
| Genotype | What it means | Typical severity |
|---|---|---|
| HbSS (sickle cell anemia) | Two copies of the sickle gene | Usually the most severe |
| HbS beta-zero thalassemia | One sickle gene, one gene that makes no normal beta-globin | Similar to HbSS |
| HbSC | One sickle gene, one hemoglobin C gene | Usually milder anemia; eye and bone problems still occur |
| HbS beta-plus thalassemia | One sickle gene, one gene that makes reduced normal beta-globin | Often milder |
| HbAS (sickle cell trait) | One sickle gene, one normal gene | A carrier state, not a disease |
Severity varies even within one genotype. Two siblings with HbSS can have very different courses, partly because of how much fetal hemoglobin (HbF) each continues to make, since HbF protects against sickling.
Symptoms and Complications
Babies are usually well at birth because fetal hemoglobin predominates. Symptoms tend to appear from around five to six months of age, as HbF falls and adult hemoglobin takes over.
- Pain crises (vaso-occlusive episodes): sudden pain in the back, chest, limbs, or abdomen, lasting hours to days.
- Dactylitis: painful swelling of the hands and feet, often the first sign in infants.
- Anemia and fatigue: a baseline hemoglobin well below normal is common in HbSS.
- Infections: the spleen is damaged early in life, leaving children vulnerable to serious bacterial infections.
- Jaundice: yellowing of the eyes from rapid red cell breakdown.
- Delayed growth and puberty in some children.
Serious complications include stroke, acute chest syndrome (a lung complication that resembles pneumonia), splenic sequestration, priapism, kidney damage, gallstones, avascular necrosis of the hip, leg ulcers, and retinal disease. Many of these are preventable or treatable when caught early, which is why regular follow-up matters so much.
Causes and Inheritance
Sickle cell disease comes from a single change in the HBB gene, which codes for the beta chain of hemoglobin. One DNA letter change swaps the amino acid glutamic acid for valine at the sixth position, and that small change is what lets HbS polymerize. You can read more about the cause of sickle cell disease and how it affects long-term outlook.
Inheritance is autosomal recessive. A child needs two abnormal beta-globin genes, one from each parent. People with one copy have sickle cell trait, which usually causes no symptoms.
When both parents have the trait, each pregnancy carries a 1 in 4 chance of a child with sickle cell disease, a 1 in 2 chance of a child with the trait, and a 1 in 4 chance of a child with neither. Those odds apply fresh to every pregnancy.
How Sickle Cell Disease Is Diagnosed
Many countries include sickle cell disease in newborn screening, using a heel-prick blood sample. A positive screen is confirmed with repeat testing, ideally before the baby is a few months old, so that preventive care can start early.
In older children and adults, the key tests are:
- Hemoglobin electrophoresis or HPLC, which separates and measures the types of hemoglobin present.
- Complete blood count (CBC), showing anemia and often a raised white cell count.
- Reticulocyte count, which is high because the marrow works hard to replace lost cells.
- Blood film, where sickled cells can be seen under the microscope.
- DNA testing of the HBB gene when results are unclear or for prenatal diagnosis.
Doctors also consider other hemoglobin disorders, such as thalassemia, which can look similar on some tests.
Treatment and Day-to-Day Management
Care aims to prevent complications, relieve symptoms, and, for some patients, cure the disease.
- Hydroxyurea: a daily oral medicine that raises fetal hemoglobin, reduces pain crises and acute chest syndrome, and is now offered to most children and adults with HbSS.
- Infection prevention: daily penicillin for young children, usually until age five, plus a full vaccine schedule including pneumococcal and meningococcal vaccines.
- Stroke screening: transcranial Doppler ultrasound in children with HbSS from age two to sixteen, with regular transfusions if results are abnormal.
- Blood transfusions: used for severe anemia, acute chest syndrome, stroke prevention, and before some surgery.
- Pain management: a written home plan, fluids, and prompt hospital care for severe episodes.
- Curative options: stem cell transplant from a matched donor, and newer gene therapies approved in some countries for selected patients.
Everyday habits help too: drinking plenty of water, dressing warmly, avoiding sudden temperature changes, pacing strenuous exercise, and keeping every scheduled appointment.
When to See a Doctor
Anyone with sickle cell disease should have an emergency plan. Seek urgent care for:
- Fever of 38.5°C (101.3°F) or higher, especially in a child
- Chest pain, cough, or trouble breathing
- Sudden weakness, facial droop, slurred speech, or severe headache
- A suddenly enlarged spleen, pale skin, or unusual sleepiness in a child
- Pain that home treatment does not control
- An erection lasting more than a few hours
Frequently Asked Questions
Can sickle cell disease be cured?
Yes, for some patients. A stem cell transplant from a matched sibling donor can be curative, and gene therapies are now an option for selected people. Both carry real risks, so they are discussed carefully with a specialist team.
Is sickle cell trait the same as sickle cell disease?
No. People with the trait carry one sickle gene and are usually healthy. The main significance is that they can pass the gene to their children.
What is the life expectancy with sickle cell disease?
Outlook has improved greatly with newborn screening, penicillin, vaccines, and hydroxyurea. Most children in high-resource settings now reach adulthood, though life expectancy is still shorter than average and depends heavily on access to care.
Can adults be diagnosed with sickle cell disease for the first time?
It is uncommon but possible, particularly with milder types such as HbSC or HbS beta-plus thalassemia, or in people born where newborn screening was unavailable. A hemoglobin electrophoresis test settles the question.
