Non-Immune Hemolytic Anemia

Medical Importance

The mature erythrocyte is a simple cell that is elegantly designed to deliver oxygen to tissues over a four-month life span; any process shortening this lifespan is called hemolysis. The physician frequently encounters patients with anemia, and one must quickly discern whether hemolysis is contributing to the anemia. In addition, patients may present with complications of chronic hemolysis without a known diagnosis, and an astute physician should recognize these complications and further evaluate the patient.

Objectives

Red Cell Degradation in the Normal State and Disease

  1. Define the terms "intravascular hemolysis" and "extravascular hemolysis" and identify which mechanism predominates in normal red cell destruction.

  2. Describe the fate of free hemoglobin following red blood cell destruction.

  3. Explain why and in what direction the following laboratory measurements are altered from normal in hemolytic anemias: serum indirect bilirubin concentration, serum LDH level, reticulocyte count, serum haptoglobin concentration, and red blood cell survival.

Classification of Hemolytic Anemias

  1. List hereditary and acquired non-immune causes of hemolytic anemia.  For the hereditary conditions, be able to describe the mode of inheritance.

Hereditary Spherocytosis (HS)

  1. Determine whether a patient may have hereditary spherocytosis (HS), given the history, physical examination, hemogram, peripheral blood smear findings, reticulocyte count, and direct antiglobulin test (direct Coomb’s test) results.

  2. Interpret the osmotic fragility test and distinguish between normal and HS red blood cells using this assay.

  3. Define the molecular basis of hereditary spherocytosis and describe the resultant structural changes to red blood cells.

Enzyme Deficiency

  1. Describe the pathway by which G6PD normally protects the red blood cell from oxidant stresses.

  2. Describe the effects of pyruvate kinase deficiency on red blood cell survival.

  3. Describe the inheritance patterns of G6PD and pyruvate kinase deficiencies.

Paroxysmal Nocturnal Hemoglobinuria (PNH)

  1. Discuss the molecular and pathophysiologic defects in paroxysmal nocturnal hemoglobinuria (PNH) and explain the test used to diagnose this disorder.

  2. List complications of PNH. 

Fragmentation Hemolysis

  1. List the causes of fragmentation hemolysis.

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