Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Anemia is an abnormally low level of red blood cells. Hemolytic anemia occurs when red blood cells are destroyed too quickly.

Red blood cells contain hemoglobin. Hemoglobin is a protein that carries oxygen in the blood.

Red blood cells are produced in the bone marrow and then released into the bloodstream. Normally, they live for 110 to 120 days. Old red blood cells are removed from the blood by the spleen and liver.

In people with hemolytic anemia, red blood cells have an abnormally short life span. There can be something wrong with the red blood cells. Or the red blood cells are normal but are destroyed by an external process.

Many different problems can cause hemolytic anemia. These include:

  • Inherited abnormalities in red blood cell membranes A red blood cell is like a little balloon filled with fluid. The balloon is the membrane that holds the fluid inside. Defects in the membrane can cause the cells to change shape. Abnormally shaped red blood cells are identified by the spleen as abnormal, and destroyed.

  • Inherited enzyme deficiencies inside red blood cells Enzymes are proteins. Certain abnormal enzyme levels cause red blood cells to become fragile. They are prone to being destroyed too quickly.

  • Hemoglobin disorders Hemoglobins are proteins that carry oxygen. Some people inherit a gene that makes an abnormal kind of hemoglobin. Hemoglobin disorders include sickle cell anemia and the thalassemias. Hemoglobin disorders can cause red blood cells to be destroyed easily.

  • Physical damage to red blood cells Hemolytic anemia can occur when red blood cells are damaged:

    • During heart-lung surgery

    • As they flow near devices placed inside the body, especially artificial heart valves

    • If they are exposed to extreme heat, as in a patient with severe burns

  • Autoimmune hemolytic anemia This occurs when the body's immune system mistakenly destroys its own red blood cells. Autoimmune hemolytic anemia can be caused by:

    • autoimmune conditions such as lupus

    • certain types of infections

    • certain medications

  • Hypersplenism The spleen is enlarged and overactive. It traps circulating red blood cells and destroys them before they are old.

In some cases, it has no clear cause.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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