Unraveling thalassemia intermedia: Novel insights of a hemoglobin Jax [HBA2:c.44G>C] and deletional α⁰-thalassemia interaction phenotype

Objective:  To elucidate the molecular basis, hematological features, and electrophoretic and chromatographic mobility behavior of an unstable α₂-globin chain variant, and to describe the diagnostic approach.

Methods:  A Thai patient with unexplained chronic anemia and her daughter were investigated. Hematological data were analyzed using a standard automated cell counter. Hemoglobin was analyzed using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Mutational analysis was performed using appropriate polymerase chain reaction (PCR) techniques and direct sequencing. Additionally, α-globin haplotype analysis was conducted. Simple and rapid diagnostic methods were developed.

Results:  Hemoglobin analysis in the patient revealed anomalous peaks separated from normal hemoglobin visible using the HPLC technique. These peaks were virtually absent in the daughter. DNA analysis identified a G to C mutation at codon 14 of the α₂-globin gene responsible for hemoglobin Jax in trans to the α⁰-thalassemia gene in the patient. Heterozygosity of this mutation was identified in her daughter. Hematological analysis showed mild thalassemia-like changes in simple heterozygotes and exhibited a hemoglobin H-like phenotype when combined with (α⁰-thalassemia. Isopropanol stability testing and bioinformatic software indicated that the variant was unstable and potentially damaging. This mutation was confirmed using allele-specific PCR. Hemoglobin Jax was strongly associated with the haplotype [+ - S + - + -].

Conclusions:  Hemoglobin Jax, a pathological α-globin variant, is asymptomatic in simple heterozygotes and demonstrates more pronounced clinical effects when associated with deletional ( -thalassemia. This knowledge can help develop strategies to prevent hemoglobinopathies in regions of high prevalence. Accurate identification requires DNA level analysis.

Keywords:
Unstable hemoglobin; Alpha-thalassemia; Hemoglobin H disease; High-performance liquid chromatography; Capillary Electrophoresis