Alpha Thalassemia

Aka: Alpha Thalassemia, Hemoglobin H Disease, HbH Disease, Hemoglobin H Constant Spring Thalassemia, Non-Immune Hydrops Fetalis, Alpha Thalassemia Trait, Alpha Thalassemia Minor, Alpha Thalassemia Intermedia, Alpha Thalassemia Major, Hemoglobin Bart's Hydrops Syndrome

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II. Epidemiology: Ethnicity

  1. African descent (2% Incidence)
  2. Asian patients (Incidence common)

III. Pathophysiology

  1. See Hemoglobin Production
  2. Autosomal Recessive trait affecting two genes on each of the two Chromosome 16
  3. Results in decrease of absence of Hemoglobin Alpha chains and excess of beta chains
  4. Images
    1. hemoglobin.jpg

IV. Types

  1. Asymptomatic
    1. Alpha Thalassemia Silent Carrier (Alpha Thalassemia Minima)
      1. Chromosome 16 gene deletions: 1 of 4
      2. Normal Hemoglobin And Hematocrit
    2. Alpha Thalassemia Trait (Alpha Thalassemia Minor)
      1. Chromosome 16 gene deletions: 2 of 4
      2. Peripheral Smear shows microcytosis
      3. Typically no Anemia (although Hemoglobin may be borderline low)
      4. MCV <80 fl
  2. Moderate to severe symptoms
    1. Alpha Thalassemia Intermedia (Deletional HbH Disease)
      1. Significant Hemoglobin H present (Hemoglobin composed of 4 beta chains)
      2. Chromosome 16 gene deletions: 3 of 4
      3. Mild to moderate Anemia (Hgb 6.9 to 10.7 g/dl, MCV 46 to 76 fl), with ineffective Erythropoiesis
      4. Associated with skeletal abnormalities
    2. Hemoglobin Constant Spring (Non-Deletional HbH Disease)
      1. Mutant Allele results in decreased alpha-globin activity
      2. Reduced alpha globin output
      3. More severe than deletional HbH
      4. Moderate to severe Anemia (Hgb 6.9 to 10.7 g/dl, MCV 48 to 80 fl) often requiring transfusion
      5. Also associated Splenomegaly, Gallstones, growth retardation, decreased Bone Mineral Density
    3. Alpha Thalassemia Major (Hemoglobin Bart, Non-Immune Hydrops Fetalis)
      1. Significant Hemoglobin Bart's present (Hemoglobin composed of 4 gamma chains)
      2. Chromosome 16 gene deletions: 4 of 4
      3. Results in Non-Immune Hydrops Fetalis (lethal in most cases)
      4. Transfusion dependent if survives

V. Signs

  1. Splenomegaly
    1. Seen in Alpha Thalassemia Intermedia and higher

VI. Labs

  1. See Thalassemia
  2. Microcytosis
    1. Seen in Alpha Thalassemia Trait and higher
  3. Hemolytic Anemia
    1. Seen in Alpha Thalassemia Intermedia and higher
    2. Typically more mild Anemia than seen in Beta Thalassemia
  4. Hemoglobin Electrophoresis
    1. See Thalassemia for findings

VII. Management

  1. See Thalassemia

VIII. Complications

  1. See Thalassemia
  2. Alpha Thalassemia Intermedia
    1. Mild to moderate Hemolytic Anemia
  3. Alpha Thalassemia Major
    1. Non-Immune Hydrops Fetalis in utero (fatal)
    2. In-Utero transfusions have been performed to prevent Non-Immune Hydrops Fetalis

IX. References

  1. Baird (2022) Am Fam Physician 105(3): 272-80 [PubMed]
  2. Chui (2003) Blood 101(3):791-800 [PubMed]
  3. Muncie (2009) Am Fam Physician 80(4): 339-44 [PubMed]
  4. Piel (2014) N Engl J Med 371(20): 1908-16 [PubMed]

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