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Hemolytic anemia
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Hemolytic anemia is anemia due to hemolysis, the abnormal breakdown of red blood cells (RBCs) either in the blood vessels (intravascular hemolysis) or elsewhere in the body (extravascular). It has numerous possible causes, ranging from relatively harmless to life-threatening. The general classification of hemolytic anemia is either acquired or inherited. Treatment depends on the cause and nature of the breakdown.
In a healthy person, a red blood cell survives 90 to 120 days (on average) in the circulation, so about 1% of human red blood cells break down each day.
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Encyclopedia
Hemolytic anemia is anemia due to hemolysis, the abnormal breakdown of red blood cells (RBCs) either in the blood vessels (intravascular hemolysis) or elsewhere in the body (extravascular). It has numerous possible causes, ranging from relatively harmless to life-threatening. The general classification of hemolytic anemia is either acquired or inherited. Treatment depends on the cause and nature of the breakdown.
In a healthy person, a red blood cell survives 90 to 120 days (on average) in the circulation, so about 1% of human red blood cells break down each day. The spleen (part of the reticulo-endothelial system) is the main organ which removes old and damaged RBCs from the circulation. In healthy individuals, the break down and removal of RBCs from the circulation is matched by the production of new RBCs in the bone marrow.
In conditions where the rate of RBC breakdown is increased, the body initially compensates by producing more RBCs; however, breakdown of RBCs can exceed the rate that the body can make RBCs, and so anemia can develop. Bilirubin, a breakdown product of hemoglobin, can accumulate in the blood causing jaundice, and be excreted in the urine causing the urine to become a dark brown colour.
Symptoms
Signs of anemia are generally present (fatigue, later heart failure). Jaundice may be present.
- certain aspects of the medical history can suggest a cause for hemolysis (drugs, fava bean or other sensitivity, prosthetic heart valve, or another medical illness)
Tests
- Peripheral blood smear microscopy:
- fragments of the red blood cells ("schistocytes") can be present
- some red blood cells may appear smaller and rounder than usual (spherocytes)
- Reticulocytes are present in elevated numbers. This may be overlooked if a special stain is not used.
- The level of unconjugated bilirubin in the blood is elevated. This may lead to jaundice.
- The level of lactate dehydrogenase (LDH) in the blood is elevated
- Haptoglobin levels are decreased
- If the direct Coombs test is positive, if hemolysis is caused by an immune process.
- Haemosiderin in the urine indicates chronic intravascular haemolysis. There is also urobilinogen in the urine.
Clinical findings in haemolytic anaemias:
1. increased serum bilirubin levels in blood, therefore jaundice
2. pallor in mucous membrane and skin
3. increased urobilinogen in urine
4. Splenomegaly
5. Pigmented gallstones may be found.
Classification of hemolytic anemias
Causes of hemolytic anemia can be either genetic or acquired.
Genetic
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Genetic causes can involve the RBC membrane, metabolism, or hemoglobin conditions.
Acquired
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Acquired hemolytic anemia can be divided into immune and non-immune mediated.
Differential diagnosis
Therapy
Definitive therapy depends on the cause.
- Symptomatic treatment can be given by blood transfusion, if there is marked anemia.
- In severe immune-related hemolytic anemia, steroid therapy is sometimes necessary.
- Sometimes splenectomy can be helpful where extravascular hemolysis is predominant (ie most of the red blood cells are being removed by the spleen).
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