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Peripheral smear result in. Beta thalassemia

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Peripheral Smear Findings in Beta Thalassemia

The peripheral smear findings differ significantly depending on whether the patient has beta thalassemia minor (trait), intermedia, or major.

Beta Thalassemia Major

CBC: Severe anemia with Hb 30-65 g/L, MCV 48-72 fL, MCH 23-32 pg.
Peripheral smear shows:
FindingExplanation
MicrocytesReduced beta-globin → small, poorly hemoglobinized cells
HypochromiaInsufficient HbA formation; large central pallor area
MacrocytesAlso present (mixed picture)
Target cells (codocytes)May have a bridge joining central and peripheral pigment zones
Nucleated red blood cells (NRBCs / normoblasts)Reflect intense erythropoietic drive - characteristic finding of thalassemia major/intermedia
Basophilic stippling (prominent)Residual ribosomes/RNA in poorly hemoglobinized cells
PolychromasiaReticulocytosis from compensatory erythropoiesis
PoikilocytosisBizarre cell shapes due to membrane damage by alpha-chain precipitates
Occasional spherocytesFrom membrane damage
Schistocytes (occasional)Fragmented cells from mechanical hemolysis
"A characteristic markedly abnormal RBC morphology is noted on the peripheral blood smear; this includes a large number of microcytes and/or macrocytes, prominent basophilic stippling, numerous target cells, which may have a bridge joining the central and peripheral pigment zones, polychromasia, and occasional spherocytes, schistocytes, and nucleated red cells."
  • Tietz Textbook of Laboratory Medicine, 7th ed.
Peripheral blood smear of beta-thalassemia major showing microcytes, target cells, NRBCs, and poikilocytosis
Fig. 77.11 - Peripheral blood smear in beta-thalassemia major (Tietz Textbook of Laboratory Medicine, 7th ed.)

Beta Thalassemia Minor (Trait)

These patients are usually asymptomatic with mild or absent anemia.
Peripheral smear shows:
  • Hypochromia
  • Microcytosis
  • Basophilic stippling
  • Target cells
"The peripheral blood smear typically shows hypochromia, microcytosis, basophilic stippling, and target cells."
  • Robbins, Cotran & Kumar Pathologic Basis of Disease

Beta Thalassemia Intermedia

Findings lie between those of minor and major - microcytic hypochromic cells, target cells, NRBCs (fewer than in major), basophilic stippling, and polychromasia.

Why These Findings Occur

The pathophysiology diagram below explains the mechanism:
Pathophysiology of beta-thalassemia major
Fig. 10.5 - Pathophysiology of beta-thalassemia major (Robbins & Kumar Basic Pathology)
  1. Reduced beta-globin synthesis → inadequate HbA → microcytic, hypochromic cells
  2. Excess unpaired alpha-globin chains form toxic precipitates → membrane damage → bizarre shapes (poikilocytosis, schistocytes, spherocytes)
  3. Massive ineffective erythropoiesis - most erythroblasts die in the marrow → NRBCs released into circulation
  4. Compensatory erythropoietic drive → polychromasia, reticulocytosis

Summary Table

FeatureMajorIntermediaMinor (Trait)
Microcytosis/Hypochromia++++++
Target cells++++++
Basophilic stippling++++++
NRBCs+++ (characteristic)+Absent
Poikilocytosis+++++Mild
Polychromasia+++Minimal
Schistocytes/SpherocytesOccasionalRareAbsent
Key distinguishing point: Circulating nucleated red blood cells (NRBCs) that are poorly hemoglobinized are characteristic of beta-thalassemia major and intermedia, and help distinguish them from iron deficiency anemia (which has similar microcytic/hypochromic morphology but no NRBCs).
Sources: Tietz Textbook of Laboratory Medicine (7th ed.); Robbins & Kumar Basic Pathology; Robbins, Cotran & Kumar Pathologic Basis of Disease.
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