Hb Bart’s Hydrops Fetalis Syndrome and Hb H Disease Caused by Deletional Chiang Rai (– –^CR) α⁰-Thalassemia in Two Unrelated Thai Families

Abstract

α⁰-Thalassemia (α⁰-thal) Chiang Rai (– –^CR; NC_000016.10: g.144215_188843del) was identified as a novel 44.6 kb deletional type of α-thalassemia (α-thal), removing all α-like globin genes. However, little is known about the deleterious effects of this genetic disorder, particularly when it is combined with other types of thalassemia. We performed molecular analysis of the – –^CR deletion using gap-polymerase chain reaction (gap-PCR) in two independent families residing in Phayao and Chiang Mai, Thailand, with an unknown causative mutation for Hb Bart’s hydrops fetalis syndrome and Hb H disease. Five out of seven individuals were diagnosed to be heterozygous for the – –^CR deletion. Of these, two also carried Hb H disease with compound heterozygosities for – –^CR and –α^3.7 (rightward) deletions. However, hematological parameters of the – –^CR carriers displayed microcytic hypochromic anemia that is comparable to other α⁰-thal traits. Although the prevalence of – –^CR has never been elucidated in a specific population, our study demonstrated that genotyping for – –^CR might be considered as an additional investigation for unexplained Hb Bart’s hydrops fetal syndrome and Hb H disease.

Keywords:

• α⁰-Thalassemia (α⁰-thal) Chiang Rai (– –^CR) deletion
• gap-polymerase chain reaction (gap-PCR)
• Hb Bart’s hydrops fetalis
• Hb H disease

Acknowledgements

C. Ruengdit and S. Pornprasert designed the research; C. Ruengdit and P. Khamphikham performed experiments and analyzed data; N. Jinorose provided the samples; P. Khamphikham and S. Pornprasert wrote the manuscript; S. Pornprasert conceptualized the idea and supervised the project. All authors have read and approved the final manuscript.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

C. Ruengdit was supported by a grant from the Teaching Assistant and Research Assistant (TA/RA) scholarships, Graduate School, Chiang Mai University, Chiang Mai, Thailand.