Erythrocyte Disorders: Smear Case 5: Target Cells and Associated Red Cell Abnormalities

Hemoglobin H disease

  • Hemoblobin H disease follows deletions of 3 of the 4 alpha globulin chains. Beta chains, unable to bind with insufficient numbers of alpha chains, form beta chain tetramers, or HbH.
  • These beta chain tetramers appear as numerous dot size inclusions in erythrocyte cytoplasm, best seen in supravital brilliant cresyl blue stains (lower photograph).
  • The most common molecular defect in alpha thalassemia is DELETION, not MUTATION; whereas, in beta thalassemia, the molecular defect is MUTATION.
  • Leptocytes, as illustrated in the upper photograph,(lepto, derived from a Greek word meaning thin, fine, or slight), are characteristic of HbH disease. They have thinner cell membranes than the cells we recognize as target cells. They stain more lightly than normal erythrocytes and their centers are almost colorless.Subtle changes perhaps, but worth keeping in mind

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