Immune hemolytic anemia

Definition

Immune hemolytic anemia is a condition in which there is a reduced blood cell count due to the premature destruction of red blood cells by the immune system.

Alternative Names

Anemia - immune hemolytic; Autoimmune hemolytic anemia (AIHA)

Causes, incidence, and risk factors

Immune hemolytic anemia occurs when antibodies form against the body's own red blood cells. The antibodies will destroy the blood cells because the immune system mistakenly recognizes these blood cells as foreign material within the body. The antibodies may be caused by:

• Blood transfusion
• Complicaton of a disease
• Pregnancy (if the baby's blood type is different from the mother's)
• Reaction to medications

If the cause of antibody formation is disease or medication, it is referred to as secondary immune hemolytic anemia. If the cause is unknown, it is called idiopathic autoimmune hemolytic anemia. This type of anemia accounts for one-half of all immune hemolytic anemias.

Risk factors are related to the causes.

Symptoms

• Dark urine
• Enlarged spleen
• Fatigue
• Pale (pallor) or yellow (jaundice) skin color
• Rapid heart rate
• Shortness of breath

Signs and tests

• Absolute reticulocyte count
• Direct or indirect Coombs' test
• Hemoglobin in the urine
• LDH (level of this enzyme rises as a result of tissue damage)
• Red blood cell count (RBC) and hemoglobin
• Serum bilirubin levels
• Serum free hemoglobin
• Serum haptoglobin

Treatment

Treatment with a steroid medication such as prednisone is usually the first therapy tried. If a steroid medication does not improve the condition, removal of the spleen (splenectomy) may be considered. Treatments with drugs that suppress the immune system (immunosuppressants) may also be given if you do not respond to steroids.

Blood transfusions, if needed for severe anemia, are given with caution because the blood may not be compatible and it may cause further hemolysis.

Expectations (prognosis)

The disease may start quickly and be very serious, or it may remain mild and not need specific treatment.

In most people, steroids or splenectomy can control anemia. In others, treatment can usually partially control the anemia.

Complications

Severe anemia rarely leads to death. Overwhelming infection may occur as a complication of treatment with steroids, other medications that suppress the immune system, or splenectomy, because these treatments reduce the body's ability to fight infection.

Calling your health care provider

Call your health care provider if you have unexplained fatigue or chest pain, or signs of infection.

Prevention

Screening for antibodies in donated blood and in the recipient may prevent hemolytic anemia related to blood transfusions.

References

Schwartz RS. Autoimmune and intravascular hemolytic anemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 164.