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beta-thalassemia-minor

Beta Thalassemia Minor: Pathogenesis and clinical findings Authors: Andrew Brack Yan Yu Huneza Nadeem Reviewers: Wendy Yao Katie Lin Liana Martel Ran (Marissa) Zhang Man-Chiu Poon* Lynn Savoie* * MD at time of publication Composition of normal adult hemoglobin (Hb): Ineffective erythropoiesis Excessive free α-chains accumulate, and α-chains precipitate in RBC precursors and RBCs These precipitants (inclusion bodies) give RBCs an abnormal shape Spleen destroys abnormally shaped RBCs Spleen accumulates destroyed red blood cells and enlarges to an abnormal size Splenomegaly (*See Splenomegaly slide for clinical findings) Mild microcytic anemia Hb: ↓ MCV: ↓ • • • 96% HbA (ααββ=2 α chains + 2 β chains) 2% HbA2 (ααẟẟ) 2% HbF (αα!!; fetal hemoglobin) Genetic point mutation on a single allele of the β globin gene on chromosome 11 (heterozygous with one normal alleleà HbA ααββ0 or ααββ+) Mild ↓ of β-chain production relative to ⍺- chain ↓ β-chain available for HbA synthesis Body compensates by ↑ production of non-affected globins (HbA , HbF) 2 ↑ HbF (nonspecific), ↑ HbA2 (hallmark sign specific to Beta Thalassemia Minor) on electrophoresis • • α-chain precipitates form structures visible under the microscope Inclusion bodies Heme from the destroyed RBCs is degraded into bilirubin and iron Excess unconjugated bilirubin is released into the blood Excess bilirubin is deposited in the skin Jaundice Excess iron is stored as ferritin ↑ or normal ferritin Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Re-Published June 8, 2022 on www.thecalgaryguide.com