Having sickle cell trait means having one gene that can cause sickle cell disease and one healthy gene. Sickle cell trait is not an illness, and it isn’t the same as sickle cell disease, or sickle cell anemia. But having sickle cell trait raises the risk of some health conditions.
According to the American Society of Hematology, between 1 million and 3 million Americans have sickle cell trait, and more than 100 million people have it worldwide. In the United States, Black Americans are most at risk.
Most people with sickle cell trait live perfectly normal lives and are in good health. However, some people experience symptoms, especially in extreme conditions like during exertion or at extreme temperatures. Some people with sickle cell trait may have complications or a higher risk of other rare illnesses.
There are usually no signs or symptoms of sickle cell trait. However, the following situations may cause problems for some people who have sickle cell trait:
Being at high altitudes (for example, when climbing a mountain or flying)
Experiencing high pressure in the atmosphere (for example, when diving)
Exercising very intensively (for example, as part of professional athletic training or military training)
Under these conditions, the red blood cells of some people with sickle cell trait can change shape and become sickled, or crescent-shaped. This can cause a range of health problems:
Blood in the urine (hematuria)
Bacteria in the urine, without causing any symptoms
Pain (cramping, muscle weakness, and a dull muscle ache)
Abdominal pain in the upper left side
Chest pain or tightness and shortness of breath
Sickle cell trait has a strong genetic or hereditary component. People with sickle cell trait have inherited one sickle cell gene and one healthy gene from their parents. In turn, they will likely pass on sickle cell trait to their children.
If both parents have sickle cell trait, their child has a 50 percent chance of inheriting sickle cell trait and a 25 percent chance of developing sickle cell disease. In the United States, sickle cell trait is most common among Black Americans: About 1 in 12 Black Americans has it.
Other ethnic and racial groups are at risk, too:
Hispanic people
South Asian people
Southern Europeans
Middle Eastern people
If one person in a family has sickle cell trait, it's often advised that the whole family be tested, so each member knows their sickle cell status.
Sickle cell trait can be diagnosed with a simple blood test. During the test, an expert will examine a drop of blood under a microscope. If they observe a sickle shape or sickling of the red blood cells, they’ll do another test called a hemoglobin electrophoresis. This test can show what hemoglobin types you have and in what percentage.
Hemoglobin is a protein found in red blood cells that gives blood its red color and helps carry oxygen throughout the body. People with sickle cell trait have a mix of hemoglobin A and hemoglobin S. Hemoglobin A is a normal type of hemoglobin, while hemoglobin S is an abnormal type that has a sickle, or crescentlike, shape.
Potential complications of sickle cell trait include the following:
Splenic infarction (cutting off of the blood supply to the spleen, which leads to dead tissue in the spleen)
Increased pressure or bleeding in the eye, which may cause trouble seeing, eye damage, glaucoma, or vision loss.
Muscle breakdown (rhabdomyolysis), especially when exercising intensely
Other conditions are associated with sickle cell trait, too:
Renal medullary carcinoma, a very rare but highly aggressive form of kidney cancer that mostly affects teens and young adults
Chronic kidney disease
Blood clots and associated complications (pulmonary embolism or deep vein thrombosis)
While most people with sickle cell trait can safely participate in sports and exercise, some athletes are at risk of health complications during physical activity, such as heat stroke and muscle breakdown. This is especially likely in extreme temperatures, high humidity, and when dehydrated.
Exercising too intensely can lead to exertional rhabdomyolysis, a condition in which skeletal muscle rapidly breaks down. Signs and symptoms of exertional rhabdomyolysis include fatigue, muscle pain, and darkened urine.
To prevent overexertion and problems associated with exercising in hot or humid conditions, take these precautions:
Drink enough fluids during games and workouts.
Follow a progressive workout plan that builds up gradually.
Rest during games and workouts.
And for training coaches and other athletic staff, recognize when a participant is in physical distress.
Sickle cell trait is not an illness, and it’s not the same as having sickle cell disease. Most people with sickle cell trait live normal lives, but some may experience symptoms, have complications, or be at a higher risk of other health conditions.
You can find out if you have sickle cell trait with a simple blood test. Because sickle cell trait can be inherited, it’s important to know your status. Speak to your healthcare provider about a genetic test.
