A large cohort of Hb H disease in northeast Thailand: A molecular revisited, diverse genetic interactions and identification of a novel mutation.

Background and Aims: To update the molecular characteristics of α-thalassemia in northeast Thailand, the molecular basis and genetic interactions of Hb H disease were examined in a large cohort of patients.
Materials and Methods: A study was done on 1,170 subjects with Hb H disease and various genetic interactions encountered during 2009-2023. Hb and DNA analyses were carried out.
Results: As many as 40 genotypes with several known, previously undescribed, and novel mutations were observed. These included 698 subjects (59.8 %) of Hb H disease, 357 (30.6 %) with EABart's disease, 63 (5.4 %) with EEBart's disease, 18 (1.7 %) with abnormal Hbs, 17 (1.5 %) with β-thalassemia, and 4 (0.4 %) with EFBart's or EFABart's disease. The molecular basis of 13 subjects (1.1 %) remains unknown. The α ⁰ -thalassemia included -- ^SEA (n = 1,139, 97.4 %) and -- ^THAI (n = 21, 1.8 %). Two rare mutations were identified in 3 subjects (0.3 %) with -- ^SA and -- ^CR deletions. For α ⁺ -thalassemia, -α ^{3.7 kb del} (n = 626, 53.5 %), Hb Constant Spring (n = 415, 35.5 %), -α ^{4.2 kb del} (n = 44, 3.8 %), Hb Paksé (n = 36, 3.1 %), and Hb Q-Thailand (n = 19, 1.6 %), were detected. Ten rarer α ⁺ -thalassemia were identified, including a novel mutation, namely the Hb Chumphae (HBA2:c.32T>A). The Hb H-Lansing-Ramathibodi, Hb H-Jax, and Hb H-Chumphae are hitherto undescribed in this region. PCR-based diagnostic methods for these α-thalassemia defects were described.
Conclusions: This study confirms the diverse heterogeneity and genetic interactions causing Hb H disease in northeast Thailand. The results should prove useful for laboratory diagnosis and genetic counseling of this genetic disorder in the region.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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