Unifying Concepts

Features of the Thalassemias

The thalassemias are a group of inherited hematologic disorders caused by defects in the synthesis of one or more of the hemoglobin chains. Alpha thalassemia is caused by reduced or absent synthesis of alpha globin chains, and beta thalassemia is caused by reduced or absent synthesis of beta globin chains. Imbalances of globin chains cause hemolysis and impair erythropoiesis.

Hematologic Indices of Iron Deficiency and Alpha and Beta Thalassemia

Test Iron Deficiency Beta Thalassemia Alpha Thalassemia
MCV (abnormal if < 80 fl in adults; < 70 fl in children six months to six years of age; and < 76 fl in children seven to 12 years of age) Low Low Low
Red blood cell distribution width High Normal; occasionally high Normal
Ferritin Low Normal Normal
Mentzer index for children (MCV/red blood cell count) > 13 < 13 < 13
Hb electrophoresis Normal (may have reduced HbA2) Increased HbA2, reduced HbA, and probably increased HbF Adults: normal Newborns: may have HbH or Hb Bart’s

Hb = hemoglobin; HbF = fetal hemoglobin; MCV = mean corpuscular volume.



  1. Martin A, Thompson AA. Thalassemias. Pediatr Clin North Am. 2013 Dec;60(6):1383-91. [Medline]
  2. Muncie HL Jr, Campbell J. Alpha and beta thalassemia. Am Fam Physician. 2009 Aug 15;80(4):339-44. [Medline]


Created: Sep 14, 2015

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