LAUSR

Sir, Krüppellike factor 1 (KLF1) is an erythroidspecific transcription factor that plays important roles in globin gene switching, erythroid lineage commitment, and erythrocyte maturation.1 Not surprisingly, the downstream effects of KLF1 mutations can result in a wide range of hematologic phenotypes. These hematologic phenotypes range from the clinically unremarkable inhibitor of Lutheran (In(Lu)) type of the Lu(ab) blood group, to a mild increase in the level of Hb F (α2γ2) or Hb A2 (α2δ2), to severe dyserythropoietic anemia and, rarely, hydrops fetalis.2 In mice, KLF1 is essential for activation of adult βglobin expression. The lethality of KLF1null mutations in mouse fetuses was attributed to severe βthalassemia.3 In humans, only one case has been reported that attributes mild βthalassemia to a KLF1 mutation.4 Here, we present another family suspected of carrying a βthalassemia trait, with an intact βglobin gene but a frameshift mutation of KLF1 gene.