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Sickle cell disease


Sickle cell disease is a group of disorders that affects hemoglobin, the molecule in red blood cells that delivers oxygen to cells throughout the body. People with this disease have atypical hemoglobin molecules called hemoglobin S, which can distort red blood cells into a sickle or crescent shape.

Signs and symptoms of sickle cell disease usually begin in early childhood. Characteristic features of this disorder include a low number of red blood cells (anemia), repeated infections, and periodic episodes of pain. The severity of signs and symptoms varies from person to person. Some people have mild health issues, while others are frequently hospitalized for more serious complications. 

The signs and symptoms of sickle cell disease are caused by the sickling of red blood cells. When red blood cells sickle, they break down prematurely, which can lead to anemia. Anemia can cause shortness of breath, fatigue, and delayed growth and development in children. The rapid breakdown of red blood cells may also cause yellowing of the skin and whites of the eyes (jaundice). Painful episodes can occur when sickled red blood cells, which are stiff and inflexible, get stuck in small blood vessels. These episodes deprive tissues and organs, such as the lungs, kidneys, spleen, and brain, of oxygen-rich blood and can lead to organ damage. A particularly serious complication of sickle cell disease is high blood pressure in the blood vessels that supply the lungs (pulmonary hypertension), which can lead to heart failure. Pulmonary hypertension occurs in about 10 percent of adults with sickle cell disease.

There are currently a range of treatment options for people with sickle cell disease. Some treatments address the symptoms of the condition, while others address the genetic cause of sickle cell disease and effectively cure the condition.  Without treatment, individuals with sickle cell disease often have lifelong health problems.


Sickle cell disease affects millions of people worldwide. It is most common among people whose ancestors come from Africa; Mediterranean countries such as Greece, Turkey, and Italy; the Arabian Peninsula; India; and Spanish-speaking regions in South America, Central America, and parts of the Caribbean.

Sickle cell disease is the most common inherited blood disorder in the United States, affecting an estimated 100,000 Americans. The disease is estimated to occur in 1 in 500 African Americans and 1 in 1,000 to 1,400 Hispanic Americans.


Variants (also called mutations) in the HBB gene cause sickle cell disease. The HBB gene provides instructions for making one part of hemoglobin. Hemoglobin typically consists of four protein subunits, two subunits of alpha-globin and two subunits of beta-globin. The HBB gene provides instructions for making beta-globin. Different variants in the HBB gene can produce abnormal versions of beta-globin. One particular HBB gene variant produces an abnormal version of beta-globin known as hemoglobin S (HbS). Other variants in the HBB gene lead to other abnormal versions of beta-globin such as hemoglobin C (HbC) and hemoglobin E (HbE). HBB gene variants can cause unusually low levels of beta-globin; this condition is called beta thalassemia.

In people with sickle cell disease, at least one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. In sickle cell anemia (also called homozygous sickle cell disease or HbSS disease), which is the most common form of sickle cell disease, hemoglobin S replaces both beta-globin subunits. In other types of sickle cell disease, just one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. The other beta-globin subunit is replaced with a different version of beta-globin, such as hemoglobin C. For example, people with hemoglobin C (HbSC) disease have hemoglobin molecules with hemoglobin S and hemoglobin C instead of beta-globin. If the variants that produce hemoglobin S and beta thalassemia occur in the same individual, that individual will have hemoglobin S-beta thalassemia (HbSBetaThal) disease.


This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • HbS disease
  • Hemoglobin S disease
  • SCD
  • Sickle cell disorders
  • Sickling disorder due to hemoglobin S

Additional Information & Resources

Genetic Testing Information

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Clinical Trials

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed


  • Ashley-Koch A, Yang Q, Olney RS. Sickle hemoglobin (HbS) allele and sickle cell disease: a HuGE review. Am J Epidemiol. 2000 May 1;151(9):839-45. doi: 10.1093/oxfordjournals.aje.a010288. Citation on PubMed
  • Cromer MK, Camarena J, Martin RM, Lesch BJ, Vakulskas CA, Bode NM, Kurgan G, Collingwood MA, Rettig GR, Behlke MA, Lemgart VT, Zhang Y, Goyal A, Zhao F, Ponce E, Srifa W, Bak RO, Uchida N, Majeti R, Sheehan VA, Tisdale JF, Dever DP, Porteus MH. Gene replacement of alpha-globin with beta-globin restores hemoglobin balance in beta-thalassemia-derived hematopoietic stem and progenitor cells. Nat Med. 2021 Apr;27(4):677-687. doi: 10.1038/s41591-021-01284-y. Epub 2021 Mar 18. Citation on PubMed
  • Gladwin MT, Sachdev V, Jison ML, Shizukuda Y, Plehn JF, Minter K, Brown B, Coles WA, Nichols JS, Ernst I, Hunter LA, Blackwelder WC, Schechter AN, Rodgers GP, Castro O, Ognibene FP. Pulmonary hypertension as a risk factor for death in patients with sickle cell disease. N Engl J Med. 2004 Feb 26;350(9):886-95. doi: 10.1056/NEJMoa035477. Citation on PubMed
  • Lattanzi A, Camarena J, Lahiri P, Segal H, Srifa W, Vakulskas CA, Frock RL, Kenrick J, Lee C, Talbott N, Skowronski J, Cromer MK, Charlesworth CT, Bak RO, Mantri S, Bao G, DiGiusto D, Tisdale J, Wright JF, Bhatia N, Roncarolo MG, Dever DP, Porteus MH. Development of beta-globin gene correction in human hematopoietic stem cells as a potential durable treatment for sickle cell disease. Sci Transl Med. 2021 Jun 16;13(598):eabf2444. doi: 10.1126/scitranslmed.abf2444. Citation on PubMed
  • Powars DR, Chan LS, Hiti A, Ramicone E, Johnson C. Outcome of sickle cell anemia: a 4-decade observational study of 1056 patients. Medicine (Baltimore). 2005 Nov;84(6):363-376. doi: 10.1097/ Citation on PubMed
  • Schnog JB, Duits AJ, Muskiet FA, ten Cate H, Rojer RA, Brandjes DP. Sickle cell disease; a general overview. Neth J Med. 2004 Nov;62(10):364-74. Citation on PubMed
  • Serjeant GR. The emerging understanding of sickle cell disease. Br J Haematol. 2001 Jan;112(1):3-18. doi: 10.1046/j.1365-2141.2001.02557.x. No abstract available. Citation on PubMed
  • Stuart MJ, Nagel RL. Sickle-cell disease. Lancet. 2004 Oct 9-15;364(9442):1343-60. doi: 10.1016/S0140-6736(04)17192-4. Citation on PubMed
  • Vichinsky E. New therapies in sickle cell disease. Lancet. 2002 Aug 24;360(9333):629-31. doi: 10.1016/S0140-6736(02)09776-3. Citation on PubMed
  • Vichinsky EP. Pulmonary hypertension in sickle cell disease. N Engl J Med. 2004 Feb 26;350(9):857-9. doi: 10.1056/NEJMp038250. No abstract available. Citation on PubMed

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