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Disease: Alpha-thalassemia

Brief Description:Alpha-thalassemia refers to a disease characterized by reduced or no production of the alpha-globin proteins that form hemoglobin.

Cause: Alpha-thalassemia is caused by changes in the alpha-globin genes on chromosome 16. Each person has four copies of this gene.

Doctors usually use blood tests to diagnose alpha-thalassemia. Because it is an inherited disease, they will also check family history. In some cases, they may order DNA testing. Thalassemia affects both males and females.

Appearance of RBCs: In patients with alpha-thalassemia, red blood cells are often smaller than normal (microcytosis; normal red blood cells are 7-8 micrometers in diameter). The size of the red blood cells usually relates to the type of alpha-thalassemia that the individual has. If a person is a silent carrier of the disease, the red blood cells may only be slightly smaller than normal. As the disease gets more severe, the red blood cells are significantly smaller than normal.

The mean corpuscular volume:RBC ratio (MCV:RBC ratio) is a way to distinguish thalassemia from other kinds of anemia. In individuals with alpha-thalassemia, the MCV:RBC ratio is less than 13. In iron deficiency anemia, the ratio is above 13.

The hematocrit (percentage of blood taken up by RBCs) is usually decreased in people with alpha-thalassemia.

The total iron-binding capacity (TIBC) is usually normal in thalassemia.

The RBC distribution width (RDW) value is normal in thalassemia. The RBCs in a sample from a patient who has thalassemia may be somewhat smaller than normal, but they are similar in size to the other cells in the sample.

Symptoms: Symptoms of alpha-thalassemia range from no or mild symptoms to severe. One form of alpha-thalassemia is almost always fatal. In general, the symptoms are more serious in patients with more nonfunctional copies of alpha-globin genes.

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