Beta Thalassemia Minor

Beta Thalassemia Minor: Pathogenesis and clinical findings
Authors: Andrew Brack Yan Yu Reviewers: Wendy Yao Katie Lin Man-Chiu Poon* Lynn Savoie* * MD at time of publication
Composition of normal adult hemoglobin (Hb): • 96% HbA (ααββ=2 α
chains+2 β chains)
• 2% HbA (ααẟẟ) 2
• 2% HbF (αα””; fetal hemoglobin)
• 0% ααβ0β+ (superscript = mutation)
• Betal thalassemia minor is common in individuals of Mediterranean and Asian descent
• No treatment required. Genetic counselling for patient and family
• Hb: ↓
• MCV: ↓
• Fe: Normal
• RBC count: Normal
• Peripheral blood film: microcytosis
basophilic stippling
• Hb electrophoresis: HbA2 ↑
(specific), HbF ↑ (nonspecific)
Excessive free α-chains accumulate, and α-chains
precipitate in RBC precursors and in RBCs
α-chain precipitates form structures visible under the microscope
Inclusion bodies
Defect in single allele of β globin gene (heterozygous with one normal allele)
Mild ↓ of β-chains relative to ⍺- chains
↓ HbA synthesis
↑ production of non-affected globins
(HbA2, HbF) to compensate
These precipitants (inclusion bodies) give RBCs an abnormal shape, resulting in the RBCs being destroyed in spleen
↑ HbF, ↑ HbA2 on electrophoresis
Ineffective erythropoiesis
Mild microcytic anemia
Heme from the destroyed RBCs are
degraded and released as bilirubin into blood àhyperbilirubinemia
Spleen accumulates destroyed red blood cells and enlarges to an abnormal size
Sign/Symptom/Lab Finding
Re-Published July 27, 2019 on