Book contents
- Frontmatter
- Contents
- List of Contributors
- Foreword, by H. Franklin Bunn
- Preface
- Introduction, by David J. Weatherall
- SECTION ONE THE MOLECULAR, CELLULAR, AND GENETIC BASIS OF HEMOGLOBIN DISORDERS
- SECTION TWO PATHOPHYSIOLOGY OF HEMOGLOBIN AND ITS DISORDERS
- SECTION THREE α THALASSEMIA
- SECTION FOUR THE β THALASSEMIAS
- 16 The Molecular Basis of β Thalassemia, δβ Thalassemia, and Hereditary Persistence of Fetal Hemoglobin
- 17 Clinical Aspects of β Thalassemia and Related Disorders
- 18 Hemoglobin E Disorders
- SECTION FIVE SICKLE CELL DISEASE
- SECTION SIX OTHER CLINICALLY IMPORTANT DISORDERS OF HEMOGLOBIN
- SECTION SEVEN SPECIAL TOPICS IN HEMOGLOBINOPATHIES
- SECTION EIGHT NEW APPROACHES TO THE TREATMENT OF HEMOGLOBINOPATHIES AND THALASSEMIA
- Index
- Plate section
- References
18 - Hemoglobin E Disorders
from SECTION FOUR - THE β THALASSEMIAS
Published online by Cambridge University Press: 03 May 2010
- Frontmatter
- Contents
- List of Contributors
- Foreword, by H. Franklin Bunn
- Preface
- Introduction, by David J. Weatherall
- SECTION ONE THE MOLECULAR, CELLULAR, AND GENETIC BASIS OF HEMOGLOBIN DISORDERS
- SECTION TWO PATHOPHYSIOLOGY OF HEMOGLOBIN AND ITS DISORDERS
- SECTION THREE α THALASSEMIA
- SECTION FOUR THE β THALASSEMIAS
- 16 The Molecular Basis of β Thalassemia, δβ Thalassemia, and Hereditary Persistence of Fetal Hemoglobin
- 17 Clinical Aspects of β Thalassemia and Related Disorders
- 18 Hemoglobin E Disorders
- SECTION FIVE SICKLE CELL DISEASE
- SECTION SIX OTHER CLINICALLY IMPORTANT DISORDERS OF HEMOGLOBIN
- SECTION SEVEN SPECIAL TOPICS IN HEMOGLOBINOPATHIES
- SECTION EIGHT NEW APPROACHES TO THE TREATMENT OF HEMOGLOBINOPATHIES AND THALASSEMIA
- Index
- Plate section
- References
Summary
INTRODUCTION
Hemoglobin E (HbE) is the most common abnormal hemoglobin in Southeast Asians, especially among the Khmer, Laotians, and Mon/Khmer speaking people, the Zhuang in Guangxi, People's Republic of China, and in India, Bangladesh, and Sri Lanka. The occurrence of HbE is most concentrated at the border of Thailand, Laos, and Cambodia, an area dubbed the HbE triangle. The gene frequency of HbE is between 0.05 and 0.10, reaching 0.5 in certain parts of Cambodia and the northeast of Thailand. It is estimated that 30 million Southeast Asians are heterozygous for HbE and 1 million are homozygous. The maintenance of so high a gene frequency indicates that the HbE variant somehow improves fitness. Correlation of HbE frequency with the incidence of malaria has been noted, suggesting the action of a balanced polymorphism. Studies of malaria and HbE are detailed in Chapter 26.
CLASSIFICATION OF HbE DISORDERS
In 1954, HbE became the fourth abnormal hemoglobin to be identified by electrophoresis, and a substitution of lysine for glutamic acid at position 26 of the β-globin chain was found in 1961. Many different syndromes are observed when HbE is variously combined with different α and β thalassemias and with other abnormal hemoglobins (Fig. 18.1). They can be classified into asymptomatic and symptomatic forms (Table 18.1).
Asymptomatic Forms
HbE Heterozygotes. HbE heterozygotes are clinically normal with minimal changes in blood counts and erythrocyte indices.
- Type
- Chapter
- Information
- Disorders of HemoglobinGenetics, Pathophysiology, and Clinical Management, pp. 417 - 434Publisher: Cambridge University PressPrint publication year: 2009
References
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