First Case of a Compound Heterozygosity for Two Nondeletional α-Thalassemia mutations, Hb Constant Spring and Hb Quong Sze.

Nondeletional α-thalassemia (α-thal) is the result of point mutations in critical regions of the α-globin genes, affecting mRNA processing, mRNA translation, or α-globin stability. Hb Constant Spring (Hb CS, HBA2: c.427T > C) is the most common nondeletional α-thal that results from a nucleotide substitution at the termination codon of the α2-globin gene. Hb Quong Sze (Hb QS, HBA2: c.377T > C) is another nondeletional α-thal in South China with the missense mutation at codon 125 of the α2-globin gene making this hemoglobin (Hb) variant highly unstable. Although homozygosity for Hb CS (α(CS)α/α(CS)α) or Hb QS (α(QS)α/α(QS)α) has been reported, clinical pictures vary from severe hemolysis that developed early in life to only mild anemia, no clinical phenotypic data of compound heterozygosity for Hb CS/Hb QS (α(CS)α/α(QS)α) has been described. In this report we describe an adult case with such a compound heterozygosity who presented with a mild α-thal.