A Number of Cases in Iran Presenting with Coinheritance of Hemoglobin-H Disease and Beta-Thalassemia Minor

Prenatal diagnosis of a rare β-thalassemia gene －90 (C>T) (HBB: c.-140 C>T) mutation associated with deletional Hb H disease (--SEA /-α4.2 )

Background

Hemoglobin H (Hb H) disease can be caused by compound heterozygosity for two different mutations or from homozygotes for mutations, and conventional genetic methods may lead to misdiagnosis when Hb H disease is combined with a rare β‐thalassemia.

Methods

Hematology parameters and hemoglobin electrophoresis analysis, gap‐polymerase chain reaction (gap‐PCR) and reverse dot‐blot hybridization (RDB‐PCR) were employed to identify common α‐thalassemia and Hb H disease. Rare β‐thalassemia mutations were detected by DNA sequencing.

Results

Hematological analysis and hemoglobin electrophoresis revealed a mild anemia α⁰‐thalassemia trait (Hb 90 g/L, MCV 71 fL, and MCH 22.7 pg) compound with β⁺‐thalassemia trait (MCV 71 fL, MCH 22.7 pg, and HbA2 5.51%) for the pregnant woman. DNA sequencing for the β‐globin gene revealed rare a －90 (C>T) (HBB: c.‐140 C>T) mutation for the woman. DNA analysis identified that the fetus inherited the α⁰‐thalassemia mutation [‐‐^SEA (Southeast Asian)] and a rare β⁺‐thalassemia mutation －90 (C>T) (HBB: c.‐140 C>T) from the mother, and the α⁺‐thalassemia mutation [‐α^4.2 (leftward)] from the father.

Conclusion

We reported a rare －90 (C>T) (HBB: c.‐140 C>T) mutation combined with the ‐‐^SEA/‐α^4.2 in a family. This finding enriched the mutation spectrum of thalassemia molecular characteristics in China and emphasized the significance in DNA sequencing in mutation screening for the families with thalassemia.

Results of Coexistence of β-Thalassemia Minor in Hb H Disease Patients

The aim of this study was to determine the hematological characteristics in a large group of Hb H (β4) patients with or without a coexisting β-thalassemia (β-thal), identified by a thalassemia screening program in mainland China. A total of 361 patients with Hb H disease were found, including 343 with deletional types and 18 with nondeletional types. β-Thalassemia was found in 28 (7.8%) out of the 361 Hb H cases, and all of the 28 cases had the deletional type of Hb H disease. Lower hemoglobin (Hb) levels were detected in cases with the nondeletional type compared to those in cases with the deletional type. β-Thalassemia significantly increases the Hb levels in Hb H cases. The Hb H and Hb Bart's (γ4) fractions were visible in 270 (85.7%) and 122 (38.7%) out of 315 deletional type cases, respectively, while no Hb H or Hb Bart's fractions were detectable in 28 deletional type cases with β-thal. Therefore, the diagnosis of Hb H disease in a β-thal carrier is challenging. Molecular analysis of α- and β-globin genes is imperative in all cases with a β-thal trait.