Hb Palencia: a novel δβδ-type two-way fusion variant with β-globin-like expression levels

Abnormal hemoglobin anti-Lepore Hong Kong compound with β0-thalassemia ameliorate thalassemia severity when co-inherited with α-thalassemia

Abnormal hemoglobin anti-Lepore Hong Kong is a rare βδ fusion variants resulting from non-homologous crossover during meiosis. Anti-Lepore Hong Kong is known to consistently exhibit significantly increased level of HbA2. In this study, we used multiplex ligation-dependent probe amplification (MLPA) and single molecular real-time (SMRT) sequencing, as well as Sanger sequencing, to identify variants in five unrelated families with abnormal elevated HbA2 level. All probands in these five families were found to be heterozygous for anti-Lepore Hong Kong. Among them, two families showed co-occurrence of β0-thalassemia and α-thalassemia (-SEA/ or αCSα/). Heterozygotes for anti-Lepore Hong Kong displayed an average HbA2 level of 17.7% and behaved normal. However, when combined with β0-thalassemia and α-thalassemia, the probands exhibited higher HbA2 level (30.2-40.8%) and behaved with β-thalassemia trait. Furthermore, determination of the α/β-mRNA ratio revealed a slight downregulation of β-globin, similar to that of β-thalassemia minor. Our study is the first to identify compound heterozygotes for anti-Lepore Hong Kong, β0-thalassemia and α-thalassemia, provide valuable information for prenatal counseling.

Hb Wanjiang: A New β-Globin Chain Variant with Two Amino Acid Substitutions (HBB: c.255_264delinsTTTTTCTCAG)

We report a new hemoglobin (Hb) variant that we have named Hb Wanjiang (HBB: c.255_264delinsTTTTTCTCAG). We identified this variant in a Chinese man by the next-generation sequencing (NGS) method. The father of the proband also carried the same variant. This variant results from a 10 bp deletion at codons 84-87 of the β-globin chain, replaced with 10 nucleotides coming from the δ-globin gene at the same position, leading to the substitution of two amino acids in the peptide chain with no change in the β-globin chain length. The heterozygotes had a normal hematological feature with no abnormal Hb variant detectable on capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). The combination of Hb Wanjiang and β-thalassemia (β-thal) was not found to aggravate anemia.