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Updated: Dec 30 2021

Thalassemias

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  • Snap Shot
    • A 22-year-old Vietnamese female presents for a routine gyn exam. Her menstrual cycle is normal and there is no evidence of other bleeding. Guiac is negative. Her hemoglobin is at 11 (12-16), RBC is 5.8 (3.5-5.5), and an MCV of 70 (80-100) with a normal RDW of 10. WBC and platelets are normal. Hemoglobin electrophoresis shows an increase in amount of Hgb A2 and Hgb F.
  • Introduction
    • Hereditary disease caused by decreased production of hemoglobin chains
    • Most common cause of microcytic anemia in Asian Americans and African Americans
    • There are four alpha genes and two beta genes that make up three forms of hemoglobin (Hgb)
        • Hgb Form
        • Subunits
        • Prevalence
        • Hgb A
        • alpha, alpha, beta, beta
        • 96-98% of adult hemoglobin
        • Hgb A2
        • alpha, alpha, delta, delta
        • Present in trace amounts in adults
        • Hgb F
        • alpha, alpha, gamma, gamma
        • Declines in the first year of life
  • STUDIES
    • Ratio used:
      • Mentzer Ratio = MCV / RBC
        • if it is less than 13 it is highly predictive of thalassemia
        • greater than 13 indicates an iron deficiency or anemia of inflammation
    • Lab findings
      • MCV - profoundly decreased
      • TIBC - decreased
      • iron - increased
      • ferretin - increased
      • reticulocyte count - increased
      • transferrin saturation - increased
  • DIAGNOSIS
    • Forms of disease diagnosed through gel-electrophoresis of globin chains
    • Unexplained finding is that although there is a decrease in the Hgb concentration and MCV, there is a normal or slightly increased RBC count
  • Alpha Thalassemia
    • Due to a decrease in alpha globin chain production
    • Seen commonly in Asians
      • less common in Africans and Mediterranean
        • Affected alleles
        • Disease
        • Characteristics
        • Evaluation
        • 1/4
        • Carrier state
        • Asymptomatic
        • Normal
        • 2/4
        • Alpha Thal. minor
        • Normal life expectancy
        • Mild microcytic anemia
        • 3/4
        • Hgb H disease
        • Associated with chronic hemolytic anemia, pallor, and splenomegaly. May require occasional transfusion
        • Hgb H (beta tetramer) and Bart's Hgb (gamma tetramer) on electrophoresis
        • 4/4
        • Hydrops fetalis
        • Fetal demise with total body edema
        • Bart's beta-4 Hgb precipitations
  • Beta Thalassemia
    • Beta thalasemia is more common in people of Mediterranean or African origin
    • Function of beta chain required at six months when switch from fetal y Hgb to adult beta Hgb occurs
        • Affected alleles
        • Disease
        • Characteristics
        • Evaluation
        • Treatment
        • 1/2
        • Asymptomatic carrier
        • Decreased Hgb A, increased Hgb A2(y) and normal Hgb F
        • Avoid oxidative stress, treat with folate and transfusions during severe anemia and pregnancy
        • 2/2
        • Thalassemia major
        • Anemia develops at six months as Hgb F declines, frontal bossing from extramedullary hematopoiesis, and splenomegly
        • No Hgb A, increased Hgb A2, and Hgb F on electrophoresis
        • Splenectomy, folate supplementation, and transfusions. Symptoms improve with transfusions, patients usually die from transfusion iron overload (heart and liver failure).
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