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Case Report

A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands

by
Faidatul Syazlin Abdul Hamid
1,
Rahimah Ahmad
1,*,
Mohamed Saleem
2,
Nur Aisyah Aziz
1,
Syahira Lazira Omar
1,
Siti Hida Hajira Mohamad Arif
1,
Jameela Sathar
3 and
Zubaidah Zakaria
1
1
Hematology Unit, Institute for Medical Research, Kuala Lumpur 50588, Malaysia
2
Regenerative Medicine Cluster, Advanced Medical and Dental Institute, University Sains Malaysia, Pulau Pinang, Malaysia
3
Hematology Department, Hospital Ampang, Selangor, Malaysia
*
Author to whom correspondence should be addressed.
Thalass. Rep. 2015, 5(1), 4675; https://doi.org/10.4081/thal.2015.4675
Submission received: 19 August 2014 / Revised: 22 April 2015 / Accepted: 18 May 2015 / Published: 21 July 2015

Abstract

We report a novel deletion at the HBA2 presented with Hb H disease in two Malaysian- Chinese patients. The two unrelated probands were diagnosed with Hb H disease in a primary hematological screening for thalassemia. Results from routine molecular analysis with gap-polymerase chain reaction (PCR) method revealed a genotype asynchrony with the observed clinical presentation. Subsequent DNA analysis using a battery of molecular methods such as gap-PCR, multiplex ligation dependent probe amplification, DNA sequencing, confirmed the presence of a novel deletion in both the index cases removing the entire α2 globin gene. We have designated the deletion as (−αMAL3.5). Hematological indices and clinical findings suggest that the deletion has an α+ phenotype. The molecular process of this deletion is the result from misalignment and unequal crossover event between the duplicated homologous Y-boxes within the α globin gene cluster. Uncharacterized deletions, single nucleotide polymorphism and other nucleotide indels at the primer binding sites may impede the optimum condition for its annealing and extension and therefore may invalidate the gap-PCR obscuring the real genotype.
Keywords: α-thalassemia; Hb H disease; thalassemia intermedia; 3.5 kb deletion; single gene deletion α-thalassemia; Hb H disease; thalassemia intermedia; 3.5 kb deletion; single gene deletion

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MDPI and ACS Style

Abdul Hamid, F.S.; Ahmad, R.; Saleem, M.; Aziz, N.A.; Omar, S.L.; Mohamad Arif, S.H.H.; Sathar, J.; Zakaria, Z. A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands. Thalass. Rep. 2015, 5, 4675. https://doi.org/10.4081/thal.2015.4675

AMA Style

Abdul Hamid FS, Ahmad R, Saleem M, Aziz NA, Omar SL, Mohamad Arif SHH, Sathar J, Zakaria Z. A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands. Thalassemia Reports. 2015; 5(1):4675. https://doi.org/10.4081/thal.2015.4675

Chicago/Turabian Style

Abdul Hamid, Faidatul Syazlin, Rahimah Ahmad, Mohamed Saleem, Nur Aisyah Aziz, Syahira Lazira Omar, Siti Hida Hajira Mohamad Arif, Jameela Sathar, and Zubaidah Zakaria. 2015. "A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands" Thalassemia Reports 5, no. 1: 4675. https://doi.org/10.4081/thal.2015.4675

APA Style

Abdul Hamid, F. S., Ahmad, R., Saleem, M., Aziz, N. A., Omar, S. L., Mohamad Arif, S. H. H., Sathar, J., & Zakaria, Z. (2015). A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands. Thalassemia Reports, 5(1), 4675. https://doi.org/10.4081/thal.2015.4675

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