Thalassemia is a genetic blood disorder. People with thalassemia have too few red blood cells and lower than normal hemoglobin * .

What Is Thalassemia?

Thalassemia is a blood disorder that runs in families. People who have thalassemia have too few red blood cells and lower hemoglobin than normal.

What Causes Thalassemia?

Distorted red blood cells in the inherited blood disorder thalassemia. Affected red blood cells are variously shaped and fragile; they rapidly break up as they move through the body.

Distorted red blood cells in the inherited blood disorder thalassemia. Affected red blood cells are variously shaped and fragile; they rapidly break up as they move through the body.

In the case of alpha-thalassemia, one defective gene does not cause individuals to develop any of the symptoms of thalassemia, although they can go on to pass that same defective gene on to offspring. Inheriting two defective genes results in a condition called alpha-thalassemia minor, with only very mild symptoms. Three defective genes result in a condition called hemoglobin H disease, which causes moderately severe symptoms. The condition of four defective genes is termed alpha-thalassemia major or hydrops fetalis, which is fatal to offspring in utero or within a short time after birth.

In the case of beta-thalassemia, one defective gene results in betathalassemia minor, which causes mild symptoms; two defective genes result in beta-thalassemia major (also known as Cooley's anemia), which causes moderately severe symptoms. Babies with this condition are usually asymptomatic at birth but develop symptoms of the disease during their first year.

Who Gets Thalassemia?

Thalassemia is one of the most common genetic * conditions. It occurs worldwide, but most commonly affects people of Greek, Italian, Middle Eastern, Asian, and African descent. Alpha-thalassemia is particularly common among descendants of people who come from Southeast Asia, China, and the Philippines. People who already know that family members have the disease are at very high risk of having the condition themselves or of passing it on to their offspring.

Some experts believe that the genetic defects of thalassemia have persisted because the abnormal red blood cell configurations actually provide some protection against malaria * because the shape of the thalassemic red blood cells inhibits the entry of the malarial parasite into the cells. Malaria is a serious problem in all the geographic areas where thalassemia has the highest frequency.

Blood is made up of a watery substance called plasma, in which circulate the various types of blood cells: red blood cells (mainly responsible for delivering oxygen to the tissues), white blood cells (involved in immune system * response), and platelets * .

Red blood cells contain hemoglobin, a complex, iron-rich protein that is responsible for picking up oxygen molecules from the lungs, delivering oxygen to all of the tissues throughout the body, picking up carbon dioxide (a waste product) from all of the tissues, and taking the carbon dioxide back to the lungs where it can be dissipated during exhalation. Too little hemoglobin in the bloodstream is called anemia * .

Hemoglobin is made up of two types of protein chains, called alpha and beta chains. Defects in alpha chains result in alpha-thalassemia; defects in beta chains result in beta-thalassemia. The production of alpha chains requires four different genes * (two from each parent), whereas production of beta chains requires only two different genes (one from each parent).

What Are the Symptoms of Thalassemia?

Symptoms of thalassemia are those of anemia, including pallor, weakness, severe fatigue, shortness of breath, dizziness, fast heart rate, decreased appetite, unintentional weight loss, failure to thrive * in babies, and poor growth and development in children. Other symptoms may include jaundice * , dark urine, bloated abdomen, fevers, diarrhea, smooth swollen tongue, and abnormalities of the facial bones.

How Is Thalassemia Diagnosed?

Thalassemia may be suspected based on the presence of characteristic symptoms, as well as on knowledge of individuals’ family history. A physical examination will reveal some of the characteristic signs of thalassemia. Blood tests can be done to demonstrate red blood cell abnormalities (in shape, size, and quantity) and decreased levels of hemoglobin and iron, which is a major component of hemoglobin. Genetic testing may be performed to reveal the abnormal genes that are responsible for thalassemia.

How Is Thalassemia Treated?

Minor forms of thalassemia may have such mild symptoms that no treatment is required. In some cases, illness, stress, surgery, childbirth, or severe infections may prompt the need for a blood transfusion * .

Major forms of thalassemia may require regular blood transfusions. Unfortunately, this treatment puts recipients at high risk of accumulating too much iron in the blood, which can be damaging to multiple organs, including the heart and liver. Drugs may be required to decrease the amount of iron in the blood (called iron chelators or chelating agents). Very severe complications from thalassemia may require a bone marrow * transplant or stem cell transplant.

Can Thalassemia Be Prevented?

People who know that thalassemia runs in their families can undergo genetic counseling to ascertain their own risk of passing the condition on to their offspring. Once a baby has been conceived, prenatal tests can determine whether the fetus has the disease. Tests include chorionic villus sampling * or amniocentesis * .

Assisted reproductive technology can also be used to try to avoid conceiving babies who have the genes for thalassemia. This technology requires in vitro * fertilization. Blastoplasts (cell masses that can develop into embryos) are tested for the presence of the thalassemia-causing genes, and only those without these genes (usually two) are then implanted into the woman's uterus.

See also Anemia, Bleeding, and Clotting • Genetic Diseases: Overview


Books and Articles

Sammarco, Serafina. Isabella's Journey: Her Battle with the Blood Disorder, Thalassemia Major. Bloomington, IN: Balboa Press, 2014.

Yaish, Hassan M. “Pediatric Thalassemia.” Medscape, April 24, 2013. (accessed November 17, 2015).


MedlinePlus. “Thalassemia.” U.S. National Library of Medicine. (accessed November 17, 2015).

National Human Genome Research Institute. “Learning About Thalassemia.” (accessed November 17, 2015).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 888-674-6854. Website: (accessed November 17, 2015).

Cooley's Anemia Foundation. 330 Seventh Ave., No. 900, New York, NY 10001. Telephone: 212-279-8090. Website: (accessed November 17, 2015).

March of Dimes. 1275 Mamaroneck Ave., White Plains, NY 10605. Telephone: 914-997-4488. Website: (accessed November 17, 2015).

* hemoglobin (HE-muh-glo-bin) is the oxygen-carrying pigment of the red blood cells.

* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.

* malaria (mah-LAIR-e-uh) is a disease spread to humans by the bite of an infected mosquito.

* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.

* platelets (PLATE-lets) are tiny disk-shaped particles within the blood that play an important role in clotting.

* anemia (uh-NEE-me-uh) is a blood condition in which there is decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.

* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* failure to thrive is a condition in which an infant fails to gain weight and grow at the expected rate.

* jaundice (JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver. An increase in bilirubin may indicate disease of the liver or certain blood disorders.

* blood transfusion is the process of giving blood (or certain cells or chemicals found in the blood) to a person who needs it due to illness or blood loss.

* bone marrow is the soft tissue inside bones where blood cells are made.

* chorionic villus sampling (KORee-on-ik VIL-lus sampling) is a test in which a small tube is inserted through the cervix and a small piece of the placenta supporting the fetus is removed for genetic testing.

* amniocentesis (am-nee-osen-TEE-sis) is a test in which a long, thin needle is inserted in the mother's uterus to obtain a sample of the amniotic fluid from the sac that surrounds the fetus. The fetal cells in the fluid are then examined for genetic defects.

* in vitro means in the laboratory or other artificial environment rather than in the living body.

  This information is not a tool for self-diagnosis or a substitute for professional care.