Hemolytic Anemia
| Overview |
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- Hemolytic Anemias are characterized by abnormal shortening of the normal erythrocyte life-span which can be caused by defects within the erythrocytes themselves or due to external factors.
| Pathogenesis |
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- Overview
- A wide variety of etiologies can result in hemolytic anemias; however, causes can be categorized based on whether the defect is intrinsic or extrinsic to the erythrocyte and the location of erythrocyte destruction.
- Intrinsic vs Extrinsic
- Intrinisic hemolytic anemias are due to defects within the erythrocytes themselves. As such, these erythrocytes would continue to show a reduced lifespan even in a different host. Examples include Glucose-6-Phosphate Dehydrogenase Deficiency, Paroxysmal Nocturnal Hemoglobinuria, Hereditary Spherocytosis, Sickle Cell Disease
- Extrinsic hemolytic anemias are due to defects external to the erythrocytes. As such, these erythrocytes would show a normal lifespan in a healthy host. Examples include Autoimmune Hemolytic Anemia, Microangiopathic Hemolytic Anemias, Disseminated Intravascular Coagulation.
- Intravascular vs Extravascular Hemolysis
- Depending on the etiology, hemolysis may occur within the blood stream itself (intravascular) or be caused by increased destruction by the reticuloendothelial system. These differing locations of blood cell destruction can be distinguished by certain laboratory assays although in many cases disease result in a mix of the two.
| Laboratory Features |
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- Reticulocytosis: In the absence of bone marrow suppression, hemolytic anemias are typically accompanied by a compensatorily increase in erythropoiesis, detected as increased levels of reticulocytes.
- Increased LDH: Destruction of erythrocytes leads to release of LDH into the periphery, a fairly non-specific sign of hemolysis
- Reduced Haptoglobin: Haptoglobin is a plasma molecule that binds free hemoglobin and reduced haptoglobin levels are a highly specific marker of hemolysis.
- Indirect Hyperbilirubinemia: Hemolysis results in release of unconjugated biliurubin and thus an indirect hyperbilirubinemia which can yield jaundice
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