Sickle Cell

Sickle cell disease is a group of inherited disorders that affects red blood cells. According to the American Society of Hematology, sickle cell disease affects up to 100,000 people in the United States and around 8% of all African Americans.

What Is Sickle Cell Disease?

Hemoglobin is a protein in red blood cells that helps carry oxygen throughout the body. Healthy red blood cells are round and flexible, but sickle cell disease stiffens and distorts these cells into a “C” or sickle shape.

Sickle-shaped cells have a harder time flowing through small blood vessels. They become stuck and block blood flow, leading to health problems.

Causes of Sickle Cell Disease

Sickle cell disease is caused by a hereditary mutation in a gene responsible for hemoglobin production. The normal gene is called hemoglobin A, or HbA, while the sickle cell gene is hemoglobin S, or HbS. Additional abnormal hemoglobin genes are also involved in some forms of sickle cell disease.

Types of sickle cell disease

There are several types of sickle cell disease, depending on the combination of hemoglobin genes an individual has inherited. The most common types include:

  • sickle cell trait (SCT): one HbA and one HbS gene
  • sickle cell anemia (HbSS): two HbS genes
  • sickle hemoglobin-C disease (HbSC): one HbS and one hemoglobin C (HbC) gene
  • sickle beta thalassemia: one HbS and one beta-thalassemia gene (another form of anemia)

Rarer types of sickle cell disease involve one HbS gene and one other abnormal hemoglobin gene (D, E or O).

Risk Factors for Sickle Cell Disease

People most at risk for sickle cell disease include:

  • People of African ancestry, including African Americans
  • People of Asian, Indian, Middle Eastern and Mediterranean descent
  • Latin Americans, descended from Mexico, Central and South America

Signs and Symptoms of Sickle Cell Disease

Symptoms of sickle cell disease and their severity depend on the type, and may include:

  • anemia symptoms such as fatigue, dizziness, irregular heartbeat
  • episodes of intense pain in the chest, abdomen or joints
  • frequent infections
  • swelling of hands and feet
  • vision problems

Sickle cell disease can also cause acute chest syndrome, a complication which occurs when red blood cells form clumps in the lungs, causing breathing difficulties, chest pain, cough, fever and low blood oxygen levels.

How Is Sickle Cell Disease Diagnosed?

Sickle cell disease is diagnosed with a blood test that looks for abnormal hemoglobin. A screening test is routinely performed on newborns. Prenatal screening may be done for unborn babies at risk for sickle cell disease.

Genetic testing can determine the exact type of sickle cell disease, or if a hidden sickle cell gene could be passed to a child.

Treatments for Sickle Cell Disease

A number of options are available to treat sickle cell disease, including:

  • antibiotics to prevent and treat infections
  • blood transfusions to boost levels of healthy red blood cells
  • fluid supplementation
  • hydroxyurea, a medication to increase healthy hemoglobin levels
  • medicine to prevent blood clots
  • pain management medications

A bone marrow transplant, also called a stem cell transplant, is a potential cure for sickle cell disease. Stem cells are basic cells that can mature into many types of specialized cells, including red blood cells. A stem cell transplant replaces unhealthy red blood cells with healthy stem cells from a genetically compatible donor, most often a sibling.

Gene therapy is another potential sickle cell disease treatment currently being researched. Approaches being investigated include replacing or repairing the defective hemoglobin gene or altering another gene’s ability to take over hemoglobin production.