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About Sickle Cell Trait

Defining the Trait

Sickle Cell Disease (SCD) and Sickle Cell Trait (SCT) are differentiated by the number of abnormal beta hemoglobin genes an individual inherits from their parents. Your genes determine what type of hemoglobin you have. Normal hemoglobin is called hemoglobin A, sickle hemoglobin is called hemoglobin S. There are numerous types of hemoglobin, that when combined with S cause sickle cell disease. The most common abnormal gene mutation produces hemoglobin S. The mutation is a change in one building block (amino acid) out of 146 that make up the hemoglobin molecule. People who inherit one sickle hemoglobin gene (S) and one normal gene (A) from their parents have sickle cell trait (AS). Sickle cell disease is the inheritance of two sickle hemoglobin genes, SS. There are several common types of sickle cell trait: AS and AC are the most common. Hemoglobin SS is the most common type of sickle cell disease in the United States followed by hemoglobin SC.

Passing Down Sickle Cell Trait

The inheritance of the sickle hemoglobin gene depends on the hemoglobin genes of the parents of a child. Sickle hemoglobin is inherited and is not contagious. Inheriting one sickle hemoglobin gene (S) and one normal gene (A) means you have sickle cell trait. Sickle cell trait protects infants and children against severe malaria. Sickle cell trait and disease are common in Sub-Saharan Africa and other areas of the world due to malaria. Migration, dysphoria, and marriage mean that anyone from any ethnic background could inherit the sickle cell trait and pass this down to their children.

Symptoms of Sickle Cell Trait

Sickle Cell Trait is not a lesser form of, and cannot turn into, Sickle Cell Disease. You are born with one or the other.   

In some cases, extreme conditions can cause red blood cells to “sickle” and create similar, but mostly milder, symptoms compared to Sickle Cell Disease. Most conditions have to do with blood flow and oxygen within the body and again are seen usually only in more extreme cases. Some examples of these extreme cases include the following: severe dehydration, extremely strenuous activity, and high altitudes. Although symptoms are not common and usually milder in those with SCT compared to those with SCD, these kinds of situations can cause the red blood cells to become deformed and disrupt blood flow to important regions of the body.

The Facts

  • Every state and racial/ethnic population includes people living with SCT and many are unaware of their personal sickle cell status.
  • SCT affects 1 million to 3 million Americans.
  • More than 100 million people worldwide have sickle cell trait.
  • About 1 out of every 12 (1:12) Black or African-Americans in the United States have SCT.
  • About 1 out of every 100 (1:100) Latinos or Hispanic Americans in the United States have SCT. 
  • SCT is not a disease but is a risk factor for some medical problems.
  • SCT can occur in any ethnicity due to migration and marriage.
  • SCT and the different types of sickle cell disease are inherited from parents.
  • There are many kinds of hemoglobin mutations that when combined with hemoglobin S can cause sickle cell disease.