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Overview of Sickle Cell Disease

Sickle cell disease (SCD) is a blood disorder where the body produces abnormally shaped red blood cells (RBCs).  

  • RBCs contain a protein called hemoglobin.  
  • Hemoglobin allows the RBCs to carry oxygen from the lungs to all parts of the body. 
  • Most people have the same type of hemoglobin, but the RBCs of a person with sickle cell disease contain sickle hemoglobin. 

 

SCD is associated with severe pain and complications1 that can affect the entire body.  

SCD Handbooks/Guides for caregivers:  

  • Children’s Healthcare of Atlanta Sickle Cell Disease Handbook for Patients and Families (English | Spanish) 

Why do sickled cells cause issues?

Normal red blood cells (RBCs) are round, smooth, and flat like a plate. They flow through blood vessels very easily. RBCs that carry sickle hemoglobin: 

    • Change their shape after they deliver oxygen to the body. They look like a banana or a sickle. This is how the disease got its name. 
    • Sickle cells are hard and sticky. This is because the sickle hemoglobin sticks together inside the blood cell. 
    • The sickle shape makes it harder for the sickle cells to flow smoothly through the blood vessels.  
    • The sickle cells may block blood flow to parts of the body.  
    • Areas of the body that do not receive normal blood flow can become damaged. This is what causes many of the problems from sickle cell disease. 

 

Problems from blocked blood flow can happen quickly, such as sudden pain. Other problems happen more slowly and can damage the body’s tissues and organs over time.  

Another problem with sickle cells is that they do not live as long as normal RBCs.  

    • Normal RBCs live for about 120 days (4 months). Sickle cells live for about 20 days (2 to 3 weeks).  
    • This causes anemia. Anemia means a low RBC count or low hemoglobin level.2 
    • The RBCs also break up and release hemoglobin leading to jaundice (yellow eyes), damages to blood vessels, and increased clotting.3 

Types of sickle cell disease

There are several different types4 of sickle cell disease (SCD) with varying symptoms, complications, and severities.  

The 4 most common types of SCD are:  

  • Hemoglobin SS (Hb SS or sickle cell anemia)  
  • Hemoglobin SC  
  • Hemoglobin S Beta + Thalassemia  
  • Hemoglobin S Beta 0 Thalassemia 

Hemoglobin SS (HbSS)

This is a severe form of sickle cell disease. People with HbSS  typically have problems. 
  • Hemoglobin SS is when a person gets 2 abnormal sickle cell genes, 1 from each parent 
      • The abnormal genes are S and S (SS). 
  • This form of sickle cell disease is sometimes called homozygous or hemoglobin SS disease. 
  • A person with this type of sickle cell disease may have more fetal hemoglobin.  
      • Sometimes this is referred to as “baby hemoglobin.”  
      • Higher fetal hemoglobin can decrease problems from HBSS 
  • Very high fetal hemoglobin happens in a much milder form of sickle cell disease called S-HPFH (hereditary persistence of fetal hemoglobin).2 

Hemoglobin SC (HbSC)

 HbSC is also when a person receives 2 abnormal genes, 1 from each parent.  
  • The abnormal genes are S and C. We call this Sickle cell disease SC because there is a hemoglobin S gene and a hemoglobin C gene.  
  • People with HbSC often have less anemia. 
  • Often, symptoms may not be as severe until the second decade of life (10 to 20 years old).  
  • People with HbSC are at higher risk for eye, spleen, and bone problems as they get older.2 

Hemoglobin Sickle Beta Thalassemia (HbS BetaThal)

Beta (β) Thalassemia is another type of gene a person receives from a parent who has the Thalassemia trait (Aβ). 

  • This gene affects the amount of hemoglobin made by the body. 
  • Sickle Beta (β) Thalassemia is when a person receives both the Beta (β) Thalassemia gene and the sickle cell disease gene, 1 from each parent. There are 2 forms of HbS Beta Thalassemia:  
      • (+) Thalassemia (Sβ+): People with HbS Beta + Thalassemia have a small amount of normal hemoglobin A1. This protects them from some of the problems that can happen with sickle cell disease. They may have milder disease.  
      • (0) Thalassemia (Sβ0): People with HbS Beta 0 Thalassemia have no normal hemoglobin A1 and higher hemoglobin A2 and S values. They have disease that presents like HbSS.2 

Page Navigation

  1. Complications of sickle cell disease. Centers for Disease Control and Prevention. https://www.cdc.gov/sickle-cell/complications/index.html. 
  2. Sickle Cell Disease Program. Handbook for Patients and Families. Children’s Healthcare of Atlanta. https://www.choa.org/-/media/Files/Childrens/teaching-sheets/sickle-cell-disease-handbook-for-patients-and-families.pdf?la=en&hash=07C12317CEE19B249D8EF2637E2BD7FDEF42F6F4. 
  3. Hope and Destiny: The Adult and Parent’s Guide to Sickle Cell Disease and Sickle Cell Trait. Platt AF, Eckman JR, Hsu LL. Auth. 6th Edition Hilton, Chicago, Il 2023 
  4. About sickle cell disease. Centers for Disease Control and Prevention. https://www.cdc.gov/sickle-cell/about/index.html#cdc_disease_basics_types-types. 

Indicators of an Emergency Situation

Patients and families should watch for the following conditions that need an urgent medical evaluation:
• Fever of 101° F or higher
• Chest pain
• Shortness of breath
• Increasing tiredness
• Abdominal swelling
• Unusual headache
• Any sudden weakness or loss of feeling
• Pain that will not go away with home treatment
• Priapism (painful erection that will not go down)
• Sudden vision change

Learn more about sickle cell disease

Resources from:

Arise Initiative

ASH

CDC

NIH

SCDAA