Skip banner links and go to contentU.S. Department of Health & Human Services * National Institutes of Health
National Heart, Lung, and Blood Institute:  Diseases and Conditions Index
Tell us what you think about this site
  Enter keywords to search this site. (Click here for Search Tips)  
U.S. Department of Health & Human Services National Institutes of Health Diseases and Conditions Index NIH Home NHLBI Home About This Site NHLBI Home NHLBI Home Link to Spanish DCI Tell us what you think
 DCI Home: Blood Diseases: Thalassemias: What Are ...

Skip navigation and go to content
What Are ...
Other Names
Who Is At Risk
Signs & Symptoms
Living With
Key Points

What Are Thalassemias?

Thalassemias (thal-a-SE-me-ahs) are inherited blood disorders. "Inherited" means they're passed on from parents to children through genes.

Thalassemias cause the body to make fewer healthy red blood cells and less hemoglobin (HEE-muh-glow-bin) than normal. Hemoglobin is an iron-rich protein in red blood cells. It carries oxygen to all parts of the body. It also carries carbon dioxide (a waste gas) from the body to the lungs, where it's exhaled.

People who have thalassemias can have mild or severe anemia (uh-NEE-me-uh). This condition is caused by a lower than normal number of red blood cells or not enough hemoglobin in the red blood cells.


Normal hemoglobin, also called hemoglobin A, has four protein chains—two alpha globin and two beta globin. The two major types of thalassemia, alpha and beta, are named after defects in these protein chains.

Four genes are needed to make enough alpha globin protein chains. Alpha thalassemia trait occurs when one or two of the four genes are missing. If more than two genes are missing, the result is moderate to severe anemia.

The most severe form of alpha thalassemia is known as alpha thalassemia major or hydrops fetalis. Babies with this disorder usually die before or shortly after birth.

Two genes (one from each parent) are needed to make enough beta globin protein chains. Beta thalassemia occurs when one or both genes are altered.

The severity of beta thalassemia depends on how badly one or both genes are affected. If both genes are affected, the result is moderate to severe anemia. The severe form of beta thalassemia also is known as thalassemia major or Cooley's anemia.

Thalassemias affect both males and females. They occur most often among people of Italian, Greek, Middle Eastern, Asian, and African descent. Severe forms usually are diagnosed in early childhood and are lifelong conditions.

Doctors diagnose thalassemias using blood tests. The disorders are treated with blood transfusions, medicines, and other procedures.


Treatments for thalassemias have improved greatly in the past few years. People who have moderate and severe thalassemias are now living longer and have better quality of life than before.

However, complications from thalassemias and their treatments are frequent. People who have moderate or severe thalassemias must closely follow their treatment plans. They need to take care of themselves to remain as healthy as possible.

January 2008

NextOther Names

Email this Page Email all Sections Print all Sections Print all Sections of this Topic

Skip bottom navigation and go back to top
Department of Health and Human Services National Institutes of Health National Heart, Lung, and Blood Institute
Blood Diseases | Heart and Blood Vessel Diseases | Lung Diseases | Sleep Disorders
NHLBI Privacy Statement | NHLBI Accessibility Policy
NIH Home | NHLBI Home | DCI Home | About DCI | Search
About NHLBI | Contact NHLBI

Note to users of screen readers and other assistive technologies: please report your problems here.