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Sickle cell disease - Risk Factors

Description

An in-depth report on the causes, diagnosis, and treatment of sickle cell disease.

Alternative Names

Sickle cell anemia

Risk Factors:

Sickle cell disease is inherited. People at risk for inheriting the gene for sickle cell descend from people who are or were originally from Africa and parts of India and the Mediterranean. The sickle cell gene also occurs in people from South and Central America, the Caribbean, and the Middle East. The high incidence of the sickle cell gene in these regions of the world is due to the sickle cell's ability to make red blood cells resistant to the malaria parasite:

People who inherit just a single gene are referred to as having the sickle trait. These people are protected against malaria and do not develop sickle cell disease. About 40% of people in certain parts of Africa and about 9% of African-Americans have the trait.
Those who inherit both copies of the HbS gene develop sickle cell disease. They are not protected from malaria, however. In fact, malaria is more serious in these individuals. An estimated 1 in 500 African-Americans and 1 in 1,000 - 1,400 Hispanic Americans are born with sickle cell disease.

Risk of Inheritance

The sickle cell gene for hemoglobin S (HbS) is the most common inherited blood condition in the United States. About 70,000 - 100,000 Americans -- mostly African-Americans -- have sickle cell disease. About 2 million Americans have sickle cell trait.

People inherit a pair of genes that regulate hemoglobin, with one gene coming from each parent. If two sickle genes are inherited, a person will have sickle cell disease. If a one normal hemoglobin gene and one sickle cell gene are inherited, a person will have sickle cell trait. People who have sickle cell trait are healthy and do not develop themselves sickle cell disease, but they are “carriers” who can pass the disease on to their children.

The risk of a child inheriting sickle cell disease or sickle cell trait is as follows:

If both parents have sickle cell trait (each have one normal hemoglobin gene and one sickle cell gene), the child has a 50% chance of inheriting sickle cell trait (one normal gene, one sickle cell gene), 25% chance of inheriting sickle cell disease (two sickle cell genes), and 25% chance of not inheriting either the trait or the disease (two normal genes).
If one parent has sickle cell trait (one normal gene and one sickle cell gene) and the other parent has two normal hemoglobin genes, the child has a 50% chance of inheriting sickle cell trait (one normal gene and one sickle cell gene) and a 50% of inheriting neither the trait nor the disease (two normal genes). The child is not at risk of inheriting sickle cell disease.
If one parent has sickle cell disease (two sickle cell genes) and the other parent has sickle cell trait (one normal gene, one sickle cell gene), the child has a 50% chance of inheriting sickle cell trait and a 50% chance of inheriting sickle cell disease.
If one parent has sickle cell disease and the other parent has two normal hemoglobin genes, the child has a 100% chance of inheriting sickle cell trait, but not the disease.
If both parents have sickle cell disease, the child has a 100% chance of inheriting the disease.

Resources

www.sicklecelldisease.org -- Sickle Cell Disease Association of America
www.nhlbi.nih.gov -- National Heart, Lung, and Blood Institute (NHLBI)
www.sicklecellsociety.org -- Sickle Cell Society (UK)
www.sicklecell-info.org -- NHLBI Comprehensive Sickle Cell Centers
www.clinicaltrials.gov -- Find clinical trials

References

Adams RJ, Brambilla D; Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) Trial Investigators. Discontinuing prophylactic transfusions used to prevent stroke in sickle cell disease. N Engl J Med. 2005 Dec 29;353(26):2769-78.

Bernaudin F, Socie G, Kuentz M, et al Long-term results of related myeloablative stem-cell transplantation to cure sickle cell disease. Blood. 2007 Oct 1;110(7):2749-56. Epub 2007 Jul 2.

Brawley OW, Cornelius LJ, Edwards LR, Gamble VN, Green BL, Inturrisi C, et al. National Institutes of Health Consensus Development Conference statement: hydroxyurea treatment for sickle cell disease. Ann Intern Med. 2008 Jun 17;148(12):932-8. Epub 2008 May 5.

Caboot JB, Allen JL. Pulmonary complications of sickle cell disease in children. Curr Opin Pediatr. 2008 Jun;20(3):279-87.

de Montalembert M. Management of sickle cell disease. BMJ. 2008 Sep 8;337:a1397. doi: 10.1136/bmj.a1397.

Dunlop RJ, Bennett KC. Pain management for sickle cell disease. Cochrane Database Syst Rev. 2006 Apr 19;(2):CD003350.

Fathallah H, Atweh GF. Induction of fetal hemoglobin in the treatment of sickle cell disease. Hematology Am Soc Hematol Educ Program. 2006:58-62.

Geller AK, O'Connor MK. The sickle cell crisis: a dilemma in pain relief. Mayo Clin Proc. 2008 Mar;83(3):320-3.

Gladwin MT, Vichinsky E. Pulmonary complications of sickle cell disease. N Engl J Med. 2008 Nov 20;359(21):2254-65.

Halasa NB, Shankar SM, Talbot TR, et al. Incidence of invasive pneumococcal disease among individuals with sickle cell disease before and after the introduction of the pneumococcal conjugate vaccine. Clin Infect Dis. 2007 Jun 1;44(11):1428-33. Epub 2007 Apr 18.

Lanzkron S, Strouse JJ, Wilson R, Beach MC, Haywood C, Park H, et al. Systematic review: Hydroxyurea for the treatment of adults with sickle cell disease. Ann Intern Med. 2008 Jun 17;148(12):939-55. Epub 2008 May 5.

Lee MT, Piomelli S, Granger S, et al. Stroke Prevention Trial in Sickle Cell Anemia (STOP): extended follow-up and final results. Blood. 2006 Aug 1;108(3):847-52.

Mehta SR, Afenyi-Annan A, Byrns PJ, Lottenberg R. Opportunities to improve outcomes in sickle cell disease. Am Fam Physician. 2006 Jul 15;74(2):303-10.

Platt OS. Hydroxyurea for the treatment of sickle cell anemia. N Engl J Med. 2008 Mar 27;358(13):1362-9.

Roach ES, Golomb MR, Adams R, Biller J, Daniels S, Deveber G, et al. Management of stroke in infants and children: a scientific statement from a Special Writing Group of the American Heart Association Stroke Council and the Council on Cardiovascular Disease in the Young. Stroke. 2008 Sep;39(9):2644-91. Epub 2008 Jul 17.

Singh PC, Ballas SK. Drugs for preventing red blood cell dehydration in people with sickle cell disease. Cochrane Database Syst Rev. 2007 Oct 17;(4):CD003426.

Strouse JJ, Lanzkron S, Beach MC, Haywood C, Park H, Witkop C, et al. Hydroxyurea for sickle cell disease: a systematic review for efficacy and toxicity in children. Pediatrics. 2008 Dec;122(6):1332-42.

U.S. Preventive Services Task Force. Screening for Sickle Cell Disease in Newborns: U.S. Preventive Services Task Force Recommendation Statement. AHRQ Publication No. 07-05104-EF-2, September 2007. Agency for Healthcare Research and Quality, Rockville, MD.

Wang WC. The pharmacotherapy of sickle cell disease. Expert Opin Pharmacother. 2008 Dec;9(17):3069-82.

Reviewed last on: 2/18/2009
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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