Hematology and Oncology Book

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Macrocytic AnemiaAka: Megaloblastic Anemia, Megaloblastic Macrocytic Anemia, Non-megaloblastic Macrocytic Anemia

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  1. See Also
    1. Anemia
    2. Anemia Clinical Clues
    3. Anemia Evaluation
  2. Diagnosis
    1. See Hemoglobin Cutoffs for Anemia
    2. See Hematocrit Cutoffs for Anemia
    3. Macrocytosis
      1. Mean Corpuscular Volume > 100 fl
      2. MCV cutoff varies by age and per reference
    4. Further divided based on Peripheral Smear (See below)
      1. Megaloblastic Macrocytic Anemia
      2. Non-megaloblastic Macrocytic Anemia
    5. Reflex studies usually obtained when macrocytosis identified
      1. Serum B12
      2. Serum Folate
      3. Reticulocyte Count
      4. Thyroid Stimulating Hormone (TSH)
  3. Classification: Megaloblastic Macrocytic Anemia
    1. Pathophysiology
      1. DNA synthesis disorder
      2. Affects Bone Marrow erythrocyte precursors
    2. Peripheral Smear findings:
      1. Neutrophil Hypersegmentation (>=6 lobes of nuclei)
      2. Megaloblastosis: Oval shaped Macrocytes
      3. Reticulocyte Index <1% (Reticulocytopenia)
        1. See Anemia for causes of Reticulocytosis
        2. By contrast, Reticulocytosis alone increases MCV
      4. Findings sensitive and specific (Early sign)
    3. Causes
      1. Vitamin B12 Deficiency (Pernicious Anemia)
      2. Folate Deficiency (often Alcohol related)
      3. See Medications Affecting Folate Metabolism
  4. Classification: Non-megaloblastic Macrocytic Anemia
    1. See Medication Causes of Marrow Toxicity
    2. Alcohol Abuse
    3. Emphysema
    4. Hypothyroidism
    5. Accelerated Erythropoiesis (High Reticulocyte Index)
      1. Hemolytic Anemia
      2. Post-hemorrhagic Anemia
    6. Increased RBC membrane surface area
      1. Obstructive Jaundice
      2. Hepatic disease
      3. Post-splenectomy
    7. Bone Marrow disorders
      1. Myelophthisic Anemia
      2. Myelodysplastic Anemia
      3. Aplastic Anemia
      4. Acquired Sideroblastic Anemia
  5. References
    1. Brigden (1995) Postgrad Med 97(5):171

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