This Friday marks the 10th anniversary of World Sickle Cell Day. The day is marked by community events and activities to gain awareness of sickle cell disease, a painful blood disorder.
What Is Sickle Cell Disease?
Sickle cell disease (SCD) is a group of inherited red blood cell disorders that include sickle cell anemia. Because healthy red blood cells are round and flexible, they can travel through small blood vessels easily, carrying oxygen-rich blood throughout the body. But blood cells in someone with SCD become stiff and sticky and are shaped like the letter “C,” or resembling a sickle, and cause episodes of severe pain. Sickle cells die early, which means people with SCD have a constant shortage of red blood cells, and when sickle cells travel throughout the blood stream, the C-shaped cells get stuck and impede blood flow.
Who Gets Sickle Cell Disease?
SCD affects millions of people worldwide, including about 100,000 Americans. It can affect anyone but is most common in people whose ancestors originated in sub-Saharan Africa; South America, the Caribbean, and Central America; Saudi Arabia; India; and the Mediterranean countries of Turkey, Greece, and Italy. Sickle cell disease occurs in one out of every 500 Black or African American births, and one in 13 Black or African American babies is born with the sickle cell trait. Both parents must have the trait to pass down the disease. More than 6,000 Californians have SCD, 43 percent of whom are younger than age 18.
People with SCD are at risk of complications from other diseases, including stroke, acute chest syndrome, blindness, and bone damage. Organ damage, particularly of the liver, kidney, lungs, heart, and spleen, can also result in people with SCD.
Early diagnosis and treatment are important since children with SCD have an increased risk for infection and other health problems. SCD is commonly diagnosed by a pin-prick blood test given at birth during a routine newborn screening. It can also be diagnosed before birth in babies whose parents carry the trait. Since there is no cure for sickle cell disease other than through bone marrow transplantation, treatment options focus on prevention and easing complications.
Signs of SCD include:
- Chronic anemia—lack of red blood cells, or Hb, in the body
- Unpredictable pain—blocked blood cells can cause pain and swelling in the area, referred to as a crisis
- Fatigue—constant tiredness, feeling weak, or lacking energy caused by anemia
- Jaundice—yellowing of the skin and whites of the eyes
Types of Sickle Cell Disease
People with sickle cell trait (SCT; HbAS) have inherited one sickle cell gene (“S”) and one normal gene (“A”). People with sickle cell trait typically do not experience any signs of the disease, but they can pass the trait on to their children. If both parents have SCT, there is a 50 percent chance that any of their children will have SCT and a 25 percent chance that any of their children will have sickle cell disease.
The most common types of SCD are:
- HbSS: This form occurs in people who inherit a sickle cell gene (“S”) from each parent. This combination makes up sickle cell anemia, which is the most severe form of the disease.
- HbSC: This form occurs in people who inherit one sickle cell gene (“S”) from one parent and one abnormal hemoglibin (“C”), a protein that helps red blood cells carry oxygen throughout the body, from the other. This is a milder form of SCD.
- HbS beta thalassemia: In this form, people inherit one sickle cell gene (“S”) from one parent and one beta thalassemia, a different form of anemia, from the other parent. There are two types of HbS beta thalassemia. People with Hbs beta O-thalassemia have a severe form of SCD, while those with HbS beta +-thalassemia have a milder form.
- HbSD, HbSE, and HbSO: These are rarer types of SCD. In each of these, people inherit one sickle cell gene (“S”) and one abnormal type of hemoglobin (“D,” “E,” or “O”). Severity differs with each type.
Cure for SCD
The only cure for sickle cell disease is bone marrow transplantation (BMT), in which healthy stem cells from a donor replace abnormal stem cells of a person with SCD. Bone marrow is the soft, fatty tissue in the center of bones where blood cells are made. Unfortunately, bone marrow transplantation is a high-risk procedure that can pose serious side effects, including death. A close match, which is necessary for a transplant to work, is difficult to find, but the best donors tend to be healthy siblings of someone with SCD. BMT is reserved for children with severe SCD who have not experienced much, if any, organ damage from the disease.
Hydroxyurea is the only effective drug known to prevent the formation of sickle cells. Hydroxyurea is an antimetabolite used to treat certain types of cancer by slowing or stopping the growth of abnormal cells in the body. It can cut the rate of painful sickle cell episodes in half. It is, however, a risky drug to use because it can cause a severe decrease in blood cells in bone marrow.
Parents whose likelihood of passing on sickle cell disease are encouraged to be tested, and the U.S. Preventive Services Task Force recommends all newborns be screened for SCD. For more information on sickle cell disease testing, read this article from San Diego Network of Care and contact your doctor.
Sources: Breaking the SSickle Cell Cycle, https://www.btsscycle.org/; Centers for Disease Control and Prevention, Sickle Cell Disease (SCD), https://www.cdc.gov/ncbddd/sicklecell/facts.html and https://www.cdc.gov/ncbddd/sicklecell/data.html#:~:text=SCD%20affects%20approximately%20100%2C000%20Americans,sickle%20cell%20trait%20(SCT); MedlinePlus, Hydroxyurea, https://medlineplus.gov/druginfo/meds/a682004.html; San Diego County, Sickle Cell Disease, https://www.sandiegocounty.gov/content/dam/sdc/hhsa/programs/phs/health_services_advisory_board/documents/HSAB_041615_Sickle_Cell_Disease-Adult_Care_2014.pdf; San Diego Network of Care, Sickle Cell Test, https://sandiego.networkofcare.org/mh/library/article.aspx?hwid=hw43792; Sickle Cell Society, World Sickle Cell Day, https://www.sicklecellsociety.org/wscd/.