Sickle cell disease (SCD) affects millions of people throughout the world and is particularly common among those whose ancestors came from sub-Saharan Africa; Spanish-speaking regions in the Western Hemisphere (South America, the Caribbean, and Central America); Saudi Arabia; India; and Mediterranean countries such as Turkey, Greece, and Italy.

It is estimated that:

• SCD affects 90,000 to 100,000 Americans.
• SCD occurs among about 1 out of every 500 Black or African-American births.
• SCD occurs among about 1 out of every 36,000 Hispanic-American births.
  
• SCT occurs among about 1 in 12 Blacks or African Americans.
  

SCD is a genetic condition that is present at birth. It is inherited when a child receives two sickle cell genes—one from each parent. SCD is diagnosed with a simple blood test. It most often is found at birth during routine newborn screening tests at the hospital. In addition, SCD can be diagnosed before birth. Because children with SCD are at an increased risk of infection and other health problems, early diagnosis and treatment are important. People with SCD start to have signs of the disease during the first year of life, usually around 5 months of age. Symptoms and complications of SCD are different for each person and can range from mild to severe. There is no single best treatment for all people with SCD. Treatment options are different for each person depending on the symptoms. The only cure for SCD is bone marrow or stem cell transplant. Bone marrow is a soft, fatty tissue inside the center of the bones where blood cells are made. A bone marrow or stem cell transplant is a procedure that takes healthy cells that form blood from one person—the donor—and puts them into someone whose bone marrow is not working properly. Bone marrow or stem cell transplants are very risky, and can have serious side effects, including death. For the transplant to work, the bone marrow must be a close match. Usually, the best donor is a brother or sister. Bone marrow or stem cell transplants are used only in cases of severe SCD for children who have minimal organ damage from the disease.

Sickle Cell Trait

People who inherit one sickle cell gene and one normal gene have sickle cell trait (SCT). People with SCT usually do not have any of the symptoms of sickle cell disease (SCD), but they can pass the trait on to their children. Most people with SCT do not have any symptoms of SCD, although—in rare cases—people with SCT might experience complications of SCD, such as pain crises. In their extreme form, and in rare cases, the following conditions could be harmful for people with SCT:

• Increased pressure in the atmosphere (which can be experienced, for example, while scuba diving).
• Low oxygen levels in the air (which can be experienced, for example, when mountain climbing, exercising extremely hard in military boot camp, or training for an athletic competition).
• Dehydration (for example, when one has too little water in the body).
• High altitudes (which can be experienced, for example, when flying, mountain climbing, or visiting a city at a high altitude).

More research is needed to find out why some people with SCT have complications and others do not.