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Anemia classification according to pathogensis

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anemia classification pathogenesis decreased production blood loss hemolysis authoritative

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Anemia classification according to pathogenesis

Anemia results from one or more of three basic mechanisms:

1. Blood loss

Loss of red blood cells from the body.
  • Acute blood loss
    • Trauma
    • Surgery
    • Acute gastrointestinal bleed
    • Ruptured ectopic pregnancy
  • Chronic blood loss
    • Menorrhagia
    • Chronic gastrointestinal bleeding, such as peptic ulcer, hemorrhoids, colorectal cancer
    • Hookworm infestation
    • Usually leads to iron-deficiency anemia

2. Decreased or ineffective red cell production

Bone marrow does not produce enough functional red blood cells.
  • Deficiency of raw materials
    • Iron deficiency
    • Vitamin B12 deficiency
    • Folate deficiency
    • Protein deficiency
  • Reduced erythropoietin stimulation
    • Chronic kidney disease
  • Bone marrow failure or suppression
    • Aplastic anemia
    • Drugs, chemotherapy, radiation
    • Viral infections
    • Toxins
  • Bone marrow infiltration or replacement
    • Leukemia, lymphoma, myelofibrosis
    • Metastatic cancer
    • Storage disorders
  • Ineffective erythropoiesis
    • Megaloblastic anemia
    • Myelodysplastic syndrome
    • Thalassemia
  • Anemia of chronic inflammation/disease
    • Chronic infection, autoimmune disease, malignancy
    • Iron is poorly available for erythropoiesis despite adequate body stores.

3. Increased red cell destruction: hemolytic anemia

Red cells are destroyed prematurely. The marrow usually responds with reticulocytosis, unless production is also impaired.
  • Intrinsic (intracorpuscular) causes: defect within the RBC
    • Membrane defects: hereditary spherocytosis
    • Enzyme defects: G6PD deficiency, pyruvate kinase deficiency
    • Hemoglobin disorders: sickle cell disease, thalassemia
    • Paroxysmal nocturnal hemoglobinuria
  • Extrinsic (extracorpuscular) causes: external destruction of normal RBCs
    • Immune: autoimmune hemolytic anemia, transfusion reactions, hemolytic disease of the newborn
    • Mechanical: prosthetic heart valves, microangiopathic hemolytic anemia, DIC
    • Infections: malaria
    • Hypersplenism
    • Burns, toxins
Simple flow:
Anemia = blood loss + decreased/ineffective production + increased destruction (hemolysis)
A fourth practical category is multifactorial anemia, for example chronic kidney disease with iron deficiency, or thalassemia where both reduced production and hemolysis contribute.
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