Anemia

Anemia

Updated: 07/13/2024

© Jun Wang, MD, PhD

 

General features

  • Decrease in red cell mass
    • Hemoglobin: Levels of hemoglobin in a specific volume of whole blood
    • Hematocrit: Fraction of whole blood composed of red blood cells
    • Red cell count: Quantity of red cell in a specific volume of whole blood
  • Three major groups based on RBC sizes
    • Microcytic
    • Normocytic
    • Macrocytic
  • Three major causes
    • Blood loss: acute or chronic
    • Increased red cell destruction: hemolysis
    • Reduced production: marrow failure due to genetic abnormality or nutritional deficiency

Etiology

  • Genetic abnormality
    • Hemoglobinopathies
    • RBC cytoskeletal abomorlities
    • Enzyme abnormalities
    • Fanconi anemia
  • Nutritional deficiencies: iron, VB12, folate, general malnutrition
  • Physical etiologies: trauma, burns, frostbite, prosthetic valves, etc
  • Chronic diseases: chronic infections, neoplasia, autoimmune disorders, kidney or liver diseases, etc
  • Infectious diseases: hepatitis, sepsis, malaria, etc

Key pathogenesis

  • Tissue hypoxia due to impaired red cell function of oxygen delivery

Clinical presentations

  • Associated with tissue hypoxia due to reduced oxygen carrying capacity
  • Clinical presentations depends on speed of anemia onset, levels of Hb, underlying health conditions
  • Grading based on Hb levels (g/dL)
    • Mild (≥ 10)
    • Moderate (8-10)
    • Severe (6.5-7.9)
    • Life-threatening (<6.5)
  • Mild anemia might be asymptomatic
  • Severe anemia may cause high output heart failure
  • Symptoms
    • Weakness, fatigue, shortness of breath, etc.
    • Pica (desire to eat unusual and non-dietary substances)
  • Signs
    • Pale skin/mucosa
    • Orthostatic hypotension
    • Tachypnea and tachycardia
    • Signs associated with underlying diseases (hepatosplenomegaly, etc)

Diagnostic approaches

  • Investigation of etiology and underlying disorders
  • Peripheral blood test
    • Complete Blood Count
      • RBC count
      • Reticulocytes count: Quantity of reticulocytes in a specific volume of whole blod
      • Hemoglobin
      • MCV: Mean Corpuscular Volume, size of RBC, used to define microcytic, normocytic and macrocytic anemia
      • MCH: Mean Corpuscular Hemoglobin,  leves of hemoglobin in RBCs, used to define normochromic and hypochromic anemia 
      • RDW: Red Cell Distribution Width, variation in RBC sizes, elevated in iron deficiency anemia, thalassemia, sickle cell anemia, etc
    • Morphology of RBCs 
      • Anisocytosis: High variation of RBC sizes, elevated RDW
      • Poikilocytosis, abnormal shaped RBC, >10%
      • Spherocytes: Ball-shaped RBC, no central pallor area
      • Target cells: RBC with target or bull’s eye appearance
      • Fragmented RBC
    • Morphology of white cells and platelets
  • Other lab studies
    • Nutritional panels: Iron, folate, VB12 Proliferation panel: Erythropoietin
    • Hemolytic panels: Haptoglobin, bilirubin, LDH, etc
    • Liver function and renal function tests
    • Bone marrow evaluation

Morphological classification

Classification by pathogenesis

Decreased RBC Production
  • Acquired
    • Abnormal RBC metabolism
      • Nutritional deficiency
    • Acquired bone marrow failure
      • Autoimmune aplastic anemia
      • Myelophthistic (marrow replacement): neoplasia, myelofibrosis
Increased RBC Destruction/loss: Hemolytic anemia, acute and chronic hemorrhage

Management

  • Usually outpatient settings
  • Investigation of etiology
  • Treatment of underlying causes
    • Nutritional and dietary therapies
    • Bleeding control
    • Splenectomy
    • Bone marrow and stem cell transplantation
  • Transfusion: Usually NOT indicated if HB>7g/dl, or asymptomatic

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