Sickle cell anemia

Sickle cell anemia is an inherited disorder that affects hemoglobin, a protein that enables red blood cells to carry oxygen to all parts of the body. The disorder produces abnormal hemoglobin, which causes the red blood cells to sickle or become crescent-shaped.

Sickle cell anemia is characterized by a low number of red blood cells (anemia), infection, and periodic episodes of pain, usually beginning in early childhood. Symptoms vary from person to person; some people have mild symptoms, while others are frequently hospitalized.

With this disorder, sickle-shaped red blood cells are destroyed rapidly, causing anemia. Anemia can lead to shortness of breath, fatigue, and delayed growth and development in children. The rapid breakdown of red blood cells may also cause yellowing of the eyes and skin, which are signs of jaundice. Other symptoms of sickle cell anemia occur when the stiff, inflexible sickled red blood cells get stuck in small blood vessels, depriving organs and tissues of oxygen-rich blood. A serious complication of sickle cell anemia is high blood pressure in the blood vessels that supply the lungs (pulmonary hypertension). Pulmonary hypertension occurs in about one-third of adults with sickle cell disease.

Sickle cell anemia affects millions of people worldwide. It is particularly common among people whose ancestors come from Africa, Mediterranean countries (such as Greece, Turkey, and Italy), the Arabian peninsula, India, and Spanish-speaking regions (South America, Central America, and parts of the Caribbean).

Sickle cell anemia is the most common inherited blood disorder in the United States, affecting 70,000 to 80,000 Americans. The disease occurs in approximately 1 in 500 African-American newborns and 1 in 1,000 to 1,400 Hispanic-American births.

Mutations in the HBB gene cause sickle cell anemia.

The HBB gene produces one of the subunits of hemoglobin, the protein that enables red blood cells to carry oxygen to all parts of the body. The mutated HBB gene produces defective hemoglobin, which distorts red blood cells into a sickle or crescent shape.

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.

You may find the following resources about sickle cell anemia helpful.

• NIH Publications - National Institutes of Health (2 links)
• MedlinePlus - Health Information (3 links)
• Genes and Disease - Genetic disorder summaries
• Educational resources - Information pages (10 links)
• Patient support - For patients and families (4 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• ClinicalTrials.gov - Linking patients to medical research
• PubMed - Recent literature
• OMIM - Genetic disorder catalog

See How are genetic conditions and genes named? in the Handbook.

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

anemia ; autosomal ; autosomal recessive ; carrier ; complication ; gene ; Hb ; hemoglobin ; hypertension ; infection ; jaundice ; oxygen ; protein ; pulmonary ; recessive ; red blood cell ; sign ; subunit ; symptom

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.