Profiling of 35 Cases of Hb S/Hb E (HBB: c.20A>T/HBB: c.79G>a), Disease and Association with α-Thalassemia and β-Globin Gene Cluster Haplotypes from Odisha, India

Abstract

Hb S/Hb E (HBB: c.20A>T/HBB: c.79G>A) is an uncommon variant of sickle cell disease resulting from coinheritance of Hb S and Hb E. Clinico-hematological and biochemical parameters of 35 cases of Hb S/Hb E disease were studied and compared with 70 matched cases of homozygous sickle cell disease (Hb SS) and Hb S/β-thalassemia (β-thal) with IVS-I-5 (G>C) (HBB: c.92+5G>C). The influence of α-thal and that of of β-globin gene cluster haplotypes among Hb S/Hb E disease was also studied. Statistical analysis was done using GraphPad InStat version 3.06. Of the 35 cases, 20 (57.14%) had a moderate clinical presentation. Mean lactate dehydrogenase (LDH) level, vaso-occlusive crises (VOCs) per year, and annual blood transfusion requirements were significantly lower in Hb S/Hb E cases than in the other two groups. The hemoglobin (Hb) and packed cell volume (PCV) levels were significantly high in Hb S/Hb E cases with α-thal and these cases were associated with microcytic-hypochromic anemia. α-Thalassemia did not influence clinical presentation in Hb S/Hb E cases. The β-globin gene cluster haplotypes of 70 alleles of Hb S/Hb E revealed an association of five typical haplotypes [Arab-Indian (A-I), Benin, Bantu, Cameroon and Senegal] in 95.71% cases. Hb S/Hb E disease exhibit asymptomatic to moderate phenotypic expression. However, further in-depth studies on Hb S/Hb E will help in reducing the disease burden especially in high-risk countries like India.

Keywords:

• α-Thalassemia (α-thal)
• β-globin gene cluster
• Hb S/Hb E (HBB: c.20A>T/HBB: c.79G>A)
• sickle cell disease

Acknowledgments

The authors are grateful to the Director, VIMSAR, Burla, Sambalpur, Odisha, India and the Dean and Principal, VIMSAR, for their kind support and necessary official approval. The authors also acknowledge the support of the Director, Anthropological Survey of India (AnSI), Ministry of Culture, Government of India, Kolkata, India for performing the DNA sequencing at the molecular laboratory of AnSI under the existing collaboration program. The authors are indebted to the late Dr. Dilip Kumar Patel, Associate Professor, Department of Medicine, and Project Coordinator, Sickle Cell Project (NHM Odisha), VIMSAR, Burla, Sambalpur, Odisha, India for his inestimable contribution to this study. The authors wish to thank the NHM, Odisha, India for funding the Sickle Cell Project, Odisha, India.

Disclosure statement

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