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  • Dominant β-thalassaemia with unusually high Hb A2 and Hb F caused by βCD121(−G) (HBB:c.364delG) in exon 3 of β-globin gene

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Dominant β-thalassaemia with unusually high Hb A2 and Hb F caused by βCD121(−G) (HBB:c.364delG) in exon 3 of β-globin gene
  1. Kritsada Singha1,
  2. Rossarin Karnpean2,
  3. Goonnapa Fucharoen1,
  4. Supan Fucharoen1
  1. 1 Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University, Muang, Khon Kaen, Thailand
  2. 2 College of Medicine and Public Health, Ubon Ratchathani University, Warinchamrap, Ubon Ratchathani, Thailand
  1. Correspondence to Dr Supan Fucharoen, Khon Kaen University, Centre for Research & Development of Medical Diagnostic Laboratories, Muang, Khon Kaen 40002, Thailand; supan{at}kku.ac.th

Abstract

We describe a dominant β-thalassaemia caused by a deletion of G at nucleotide position 364 in exon 3 of the β-globin gene. The heterozygosity of this mutation was found in a 36-year-old Thai patient who had moderate hypochromic microcytic anaemia with haemolytic blood picture. Haemoglobin (Hb) analysis revealed relatively higher Hbs A2 (6.8%) and F (4.7%) as compared with those of β0-thalassaemia (n=278) and β+-thalassaemia (n=55) carriers in our series. Secondary structure prediction of the elongated β-globin chain showed that the α-helix at the C-terminal is disrupted dramatically by the random coil and β-sheet, which should result in a highly unstable β-globin variant, undetectable in peripheral blood and a dominant clinical phenotypic feature.

  • genetics
  • haematology
  • haemoglobinopathy
  • molecular genetics
  • thalassaemia

https://doi.org/10.1136/jclinpath-2019-206308

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    Footnotes

    • Handling editor Mary Frances McMullin.

    • Contributors KS performed the experiment, analysed the data and developed the initial manuscript. RK helped in obtaining the patient’s specimen and collecting initial haematological and clinical information, and read the final manuscript. GF helped to design the study, supervised the research and interpreted the data, and wrote the manuscript. SF designed the experiment, facilitated the study, acquired research grant, analysed the data, and critically revised and approved the final manuscript.

    • Funding This work was supported by a grant from Khon Kaen University, Thailand. KS is supported by the Postdoctoral Training Program of the Graduate School of Khon Kaen University (Contract ID 59256), Thailand. SF is a recipient of the TRF Research Team Promotion Grant (RTA) of the Thailand Science Research and Innovation (TSRI), Thailand (Contract ID RTA6280005).

    • Competing interests None declared.

    • Patient consent for publication Obtained.

    • Ethics approval Ethical approval of the study protocol was obtained from the IRB of Khon Kaen University, Thailand (HE612242).

    • Provenance and peer review Not commissioned; externally peer reviewed.