What is thalassemia?

Red blood cells transport oxygen throughout the body; hemoglobin is the protein in red blood cells that actually carries the oxygen. Thalassemia (thal-uh-SEE-me-uh) is a group of disorders that affect the body's ability to produce normal hemoglobin.

People who have thalassemia produce fewer healthy hemoglobin proteins, and their bone marrow produces fewer healthy red blood cells.

Thalassemias can cause mild or severe anemia and other complications that can occur over time (such as iron overload). Symptoms of anemia include fatigue, difficulty breathing, dizziness, and a pale skin tone.

Who is at risk for thalassemia?

Thalassemias occur more often among certain ethnicities, including people of Italian, Greek, Middle Eastern, Asian, and African descent. Thalassemias are an inherited disorder, which means they are passed from a parent to their child.

What are the types of thalassemia?

Four protein chains make up hemoglobin — 2 alpha globin and 2 beta globin chains. There are 2 major types of thalassemia – alpha thalassemia and beta thalassemia – named after defects that can occur in these protein chains.

Alpha Thalassemia

Four genes, 2 from each parent, are required to make alpha globin protein chains. When 1 or more genes are missing, it produces alpha thalassemia. This chart describes the different types of alpha thalassemia.

  • Missing alpha genes: 1
    • Disorder: silent carrier
    • Anemia symptoms: none
    • Other names: Alpha thalassemia - 2 trait, alpha thalassemia minima
  • Missing alpha genes: 2
    • Disorder: trait
    • Anemia symptoms: mild
    • Other names: Alpha thalassemia - 1 trait, alpha thalassemia minor
  • Missing alpha genes: 3
    • Disorder: Hemoglobin H
    • Anemia symptoms: moderate
    • Other names: Hemoglobin H disease
  • Missing alpha genes: 4
    • Disorder: major
    • Anemia symptoms: fatal
    • Other names: Hydrops fetalis with Hemoglobin Barts

What are the symptoms of alpha thalassemia?

People who are missing one alpha gene (silent carriers) usually don't have any symptoms. Hemoglobin H disease often causes symptoms at birth and may cause moderate to severe lifelong anemia.

Beta Thalassemia

There are normally 2 beta globin genes, one from each parent. Beta thalassemia is a change in 1 or both of the beta globin genes. This chart describes the different types of beta thalassemia.

  • Affected beta genes:1
    • Disorder: silent carrier
    • Anemia symptoms: mild
    • Other names: Beta thalassemia minor
  • Affected beta genes: 1
    • Disorder: trait
    • Anemia symptoms: mild
  • Affected beta genes: 2
    • Disorder: intermedia
    • Anemia symptoms: moderate
  • Affected beta genes: 2
    • Disorder: major
    • Anemia symptoms: severe
    • Other names: Cooley's anemia

What are the symptoms of beta thalassemia?

Symptoms of beta thalassemia include growth problems, bone abnormalities such as osteoporosis, and an enlarged spleen (the organ in the abdomen that plays a part in fighting infection).

People with thalassemia can get too much iron in their bodies (iron overload), either from frequent blood transfusions or from the disease itself. Too much iron can cause damage to your heart, liver, and endocrine system, which includes glands that produce hormones that regulate processes throughout your body.

People who have thalassemias may suffer severe infections. One reason may be the large number of blood transfusions these patients need; the infections may be carried in the blood that they receive in a transfusion.

Last reviewed by a Cleveland Clinic medical professional on 07/14/2018.


  • National Heart, Lung, and Blood Institute. What Are Thalassemias? Accessed 3/5/2020.
  • Centers for Disease Control and Prevention. Thalassemia Accessed 3/5/2020.
  • American Academy of Family Physicians/FamilyDoctor.org. Thalassemia Accessed 3/5/2020.

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