Microcytic Anemia Disorders


  • Def:
    • Reduction in circulating RBC mass due to blood loss, destruction, or impaired production
    • Hb < 13.5 g/dl in males
    • Hb < 12.5 g/dl in females
  • Presentation:
    • Low RBCs reduces oxygen-carrying capacity:
      • -fatigue, weakness, dyspnea
      • -pale skin and conjunctive (even blue)
      • -headache, dizziness, lightheadedness
      • -angina (esp. if already have CVD)
  • Micro: MCV , 80 fl/rbc
  • Normo: MCV = 80 – 100
  • Macro: MCV > 100

Microcytic Anemia

Sideroblastic anemia (ringed sideroblasts)

Anemia of Chronic Disease

Lead poisoning (basophilic stippling)

Iron Deficiency


  • Def:
    • Microcytic anemia due to decreased production of globin chains (alpha or beta depending on which chain is deficient)
    • Lack of globins results in decreased Hb and causes the anemia
    • Also increases the amount of the “normal” globin chain, which then has nothing to bind to and precipitates, binding to and damaging the RBC membrane
    • These damaged cells are removed by the reticuloendothelial system (spleen – extravascular hemolysis)
    • Also with less heme to bind iron, toxic-free iron accumulates in the RBCs and causes death within the BM (intravascular hemolysis)
    • Usually inherited mutations/deletions that are actually beneficial against malaria.
  • Presentation:

Alpha Thalassemia

  • Def:
    • Most common hemoglobinopathy, seen in 30% of West Africans and 5-15% of SE Asians (because protects against malaria)
    • Alpha globin gene normally is duplicated, with 4 total copies – disease spectrum depends on how many of the 4 genes are dysfunctional
  • Types:
    • 1 deletion – asymptomatic
    • 2 trans deletions (opposite chromosomes) – asymptomatic but microcytic (not anemic though). Seein both black and asian populations
    • 2 cis deletions – asymptomatic but microcytic (not anemic), with a risk of severe thalassemia in offspring if other parent has one or two deletions (ONLY IN ASIA)
    • 3 deletions – Hemoglobin H disease – unbound beta chains form HbH tetramers that damage the RBCs with hypochromia, microcytosis, moderately severe hemolytic anemia, growth retardation, and iron overload
    • 4 deletions – fatal in utero – hydrops fetalis
  • Blood smear:

Hydrops fetalis

Beta Thalassemia

Beta Thalassemia Major
  • Def:
    • Homozygous for B gene deletions (B0/B0) on Ch 11
    • More severe form with severe anemia a few months after birth
    • HbF (a2y2) is temporarily protective as fetal Hb does not use B chains, but later on alpha chains form tetramers and result in reduced RBC production and severe extravascular hemolysis in the spleen
    • This leads to iron overload (which we can try to treat with chelation, BM transplants, and now splicing of mutation)
    • Lack of B chains means there is pretty much no HbA, so there is a compensatory rise in HbA2 and HbF
    • Often preset with skeletal and facial deformities due to increased RBC production (marrow expansion as it tries to make up the blood)
  • Blood smear:

Beta thalassemia minor