Thalassemia-like Phenotype in a Novel Complex Hemoglobinopathy With α, β, δ Globin Chain Abnormalities

Abstract

The occurrence of multiple abnormalities of α, β, δ, and γ globin genes may lead to unusual and complex phenotypes when they arise simultaneously in the same individual. Here, we report the findings of an African American boy who coinherited 3 heterozygous globin gene abnormalities: the unstable β-globin chain variant; hemoglobin (Hb) Showa-Yakushiji [β110(G12) Leu→Pro], the δ-globin chain variant; HbB2 [δ16(A13) Gly→Arg] and α-thalassemia (α-thal); (α-/αα). Hb Showa-Yakushiji had been previously described in Japanese, Indian, and European populations. We report its first occurrence in a child of African ancestry who presented with anemia not responsive to iron and an incomplete β-thalassemia minor phenotype. Although the clinical and laboratory features of Hb Showa-Yakushiji mimic those of a β-thalassemia, the coinheritance of the δ-globin chain variant Hb B2 suppressed the relative increase in Hb A2 usually observed in heterozygotes for the Hb Showa-Yakushiji mutation. Protein-based methods detected only a trace amount of HbB2 and failed to reveal presence of Hb Showa-Yakushiji and α-thal. The latter were only identified through DNA analyses. The diagnostic difficulties, molecular characteristics, and genotype/phenotype correlations of this novel complex hemoglobinopathy syndrome are reviewed.