Molecular Basis and Hematologic Phenotype of Hemoglobin H Disease Combined with Two Rare β-Globin Mutations

In area where α-thalassemia and β-thalassemia are prevalent, the coinheritance of hemoglobin H disease (Hb H disease) and β-thalassemia are not uncommon and could result in complex thalassemia intermedia syndromes. In this study, we investigate the hematological and molecular characteristics of two previously undescribed cases that co-inherited Hb H disease and rare β-globin gene (HBB) mutations found in Chinese populations. Proband I was a boy with Hb H disease in association with IVS-II-5(G > C) (HBB:c0.315 + 5G > C) mutation. Proband II was a boy with a combination of Hb H and Hb Zengcheng [β114(G16) Leu > Met; HBB:c.343C > A]. Both of them had mild hypochromic microcytic anemia, and neither had ever received a blood transfusion. In both cases, the level of Hb A₂ was within normal range, and no Hb H was detected, but a small amount of Hb Bart's was observed in proband I. Routine DNA analysis detected the deletional Hb H disease in both cases. IVS-II-5(G > C) (HBB:c0.315 + 5G > C) and Hb Zengcheng (HBB:c.343C > A) mutations were found by DNA sequencing of β-globin gene. The co-inheritance of Hb H disease with rare β-thalassemia may result in an atypical pattern of Hb H disease, and further investigation of rare genotypes should be conducted to avoid missed diagnosis.