Hemolytic anemia is a condition in which there are not enough red blood cells in the blood, due to the premature destruction of red blood cells. There are a number of specific types of hemolytic anemia, which are described individually.

Hemolytic anemia occurs when the bone marrow is unable to increase production to make up for the premature destruction of red blood cells. If the bone marrow is able to keep up with the early destruction, anemia does not occur (sometimes called compensated hemolysis).

There are many types of hemolytic anemia, which are classified by the reason for the premature destruction of red blood cells. The defect may be in the red blood cell itself (intrinsic factor), or outside the red blood cell (extrinsic factors).

Intrinsic factors are often present at birth (hereditary). They include:

• Abnormalities in the proteins that build normal red blood cells
• Differences in the protein inside a red blood cell that carries oxygen (hemoglobin)

Extrinsic factors include:

• Abnormal immune system responses
• Blood clots in small blood vessels
• Certain infections
• Side effects from medications

Types of hemolytic anemia include:

• Hemoglobin SC disease (similar in symptoms to sickle-cell anemia)
• Hemolytic anemia due to G6PD deficiency
• Hereditary elliptocytosis
• Hereditary ovalocytosis
• Hereditary spherocytosis
• Idiopathic autoimmune hemolytic anemia
• Malaria
• Microangiopathic hemolytic anemia (MAHA)
• Non-immune hemolytic anemia caused by chemicals or toxins
• Paroxysmal nocturnal hemoglobinuria (PNH)
• Secondary immune hemolytic anemia
• Sickle-cell anemia
• Thalassemia
• Transfusion of blood from a donor with a different blood type

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

These are tests for red blood cell destruction (hemolysis). Specific tests can identify the types of hemolytic anemia. They are usually performed when hemolysis is suspected or has been determined.

• Absolute reticulocyte count
• Free hemoglobin in the serum or urine
• Hemosiderin in the urine
• Red blood cell count (RBC) and hemoglobin
• Serum haptoglobin levels
• Serum indirect bilirubin levels
• Serum LDH
• Urine and fecal urobilinogen

Directly measuring the red cell life span with radioactive tagging techniques shows a shortened life span.

This disease may also affect the following test results, depending on the specific cause:

• AST
• Coombs' test, direct
• Coombs' test, indirect
• Donath-Landsteiner test
• Febrile or cold agglutinins
• Hematocrit
• Leukocyte alkaline phosphatase
• Peripheral blood smear
• Platelet count
• Protein electrophoresis - serum
• RBC indices
• Serum creatinine
• Serum ferritin
• Serum iron
• Serum potassium level
• Serum uric acid
• TIBC
• White blood count differential

Treatment depends on the type and cause of the hemolytic anemia. Folic acid, iron replacement, and corticosteroids may be used. In emergencies, a blood transfusion or removal of the spleen (splenectomy) may be necessary.

The outcome depends on the type and cause of hemolytic anemia.

The complications depend on the specific type of hemolytic anemia. Severe anemia can cause cardiovascular collapse. Severe anemias can aggravate heart disease, lung disease, or cerebrovascular disease.

Call for an appointment with your health care provider if you develop symptoms of hemolytic anemia.

There is no known prevention for hemolytic anemia.

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