Albinism in Africa

Historical, Geographic, Medical, Genetic, and Psychosocial Aspects

Jennifer Kromberg, Prashiela Manga, Jennifer Kromberg, Prashiela Manga

• Éditeur: Academic Press
• Année: 2018
• ISBN:
  9780128133170
• Sujet: Medicina
• Sous-sujet: Genética en medicina

Albinism in Africa: Historical, Geographic, Medical, Genetic, and Psychosocial Aspects provides the first in-depth reference for understanding and treating patients of human albinism in Africa. Leading international contributors examine the historical, geographic, psychosocial, genetic and molecular considerations of importance in effectively and sensitively managing this genetic disorder. Foundational chapters covering the historical and psychosocial aspects of albinism are supplemented by discussions of the pathobiology of the disease, as well as a thorough analysis of the genetics of skin pigmentation, eye pigmentation, hair pigmentation, and incidents of skin cancer involved in the manifestations of this disorder.

New prenatal diagnostics and genetic testing methods, genetic risk assessment for individuals, families, and communities, and novel genetic markers that may be used for developing new therapeutics for treating albinism are also discussed in detail. The book provides care management approaches that may be applied to instances of albinism in other regions, along with guiding principles for treating rare genetic disorders and stigmatized patient populations across the globe.

• Includes contributions from leading international contributors who examine the historical, geographic, psychosocial, genetic and molecular aspects of importance in sensitively managing albinism in Africa
• Discusses recent advances in our understanding of the pathobiology of albinism, while also offering a thorough analysis of the genetics of skin pigmentation, eye pigmentation, hair pigmentation, and rates of skin cancer
• Highlights new prenatal diagnostics and genetic testing methods and approaches to genetic risk assessment for individuals, families and communities

Chapter 1

Introduction and Historical Background

Jennifer G.R. Kromberg University of the Witwatersrand and National Health Laboratory Service, Johannesburg, South Africa

Abstract

In this chapter the topic of albinism in Africa is introduced, the motivation for writing a book on this condition is covered, terms used are defined, and the nature of the wide-ranging contents is described. Aspects discussed in the book include the historical background, clinical, epidemiological, molecular biology and genetics, dermatological, ophthalmologic, low-vision rehabilitation, psychosocial and cultural, genetic counseling, and genetic testing, as well as human rights, disability, marginalization, management, prevention, social support groups, and a personal perspective. The relevant historical research literature on albinism is reviewed, focusing on projects conducted in Africa. Published records of the condition start at least two millennia ago; experts suggest that Noah was the first person with albinism to be described. Thereafter, the condition has been observed and reported by travelers, explorers, doctors, and missionaries in people throughout the world. However, prevalence is generally higher in Africa than elsewhere and the health and cultural problems faced by affected people are more severe.

Keywords

Africa; African culture; Background; Genetics; History; Oculocutaneous albinism; Prevalence; Research

Outline

I. Introduction

Definitions

II. Historical Background

Studies on Albinism in Africa

0–1913

1913–51

1952–72

1973–84

1985–Date

Studies on Albinism Elsewhere in the World

III. Elucidating the Genetic and Molecular Basis of Albinism

IV. Conclusion

References

I. Introduction

Oculocutaneous albinism (OCA) is an autosomal recessive, inherited disorder that is associated with significantly reduced or absent pigmentation in the skin, hair, and eyes. It is a condition that is found in every population worldwide and encountered by health professionals and clinicians in many different specialties, fields, and situations. It has been observed and documented for at least two millennia in Africa and has also been reported widely around the world. Presently, research scientists, such as molecular geneticists, medical scientists, biologists, biochemists, and anatomical pathologists, as well as researchers in the humanities, social sciences, and other disciplines, are involved in investigating the condition on many different levels.

The general aim of this book is to cover as many of the topics and issues relevant to the common forms of OCA found in Africa as possible, from the perspective of clinicians, epidemiologists, dermatologists, ophthalmologists, medical geneticists, genetic counselors, scientists, molecular geneticists, health professionals, psychologists, sociologists, social and community workers, and anthropologists. Each topic will be discussed comprehensively, with a focus on Africa, using the available published literature, as well as the experience and expertise available in South Africa, where the condition is common and 1 in 4000 black individuals is affected (Kromberg and Jenkins, 1982). The rarer forms of albinism, such as ocular albinism (OA), which affects the eyes only, and the types associated with rare syndromes, such as Hermansky–Pudlak, Chediak–Higashi (Witkop et al., 1983), and Griscelli syndrome (Menasche et al., 2003), will be mentioned where necessary but otherwise will not be covered at length.

The book attempts to examine OCA from several different angles so as to be of use to clinicians and researchers, as well as to students of the condition and families affected by it. It also attempts to correct some of the misconceptions that surround the condition, especially the tragic one that has come to the fore recently and led to the murders of affected people for body parts, which are used as powerful medicines by traditional healers, in some countries in Central and Southern Africa.

To place albinism in context, this chapter will outline the relevant writings and research publications that have originated over many centuries and that illustrate how the knowledge on the condition slowly accumulated. In Chapters 2–4, the characteristics associated with the condition, its epidemiology and population genetics, in countries around the world, will be covered. The modern development of molecular biology, the genetics of albinism and the rapidly expanding expertise on these topics will be described in Chapter 5. The dermatological, ophthalmologic, and low-vision rehabilitation aspects will be discussed in detail in Chapters 6–8 respectively. Thereafter, because people with albinism are challenged with many psychosocial and cultural issues (including myths, superstitions, and the resulting stigmatization), several of these issues will be covered in Chapter 9. This discussion will be followed by two chapters, 10 and 11, on genetic counseling for the condition and on genetic testing, prenatal diagnosis, and the ethical and other issues associated with these procedures. Chapter 12 will deal with marginalization, disability and human rights issues, and community work undertaken to advance the rights of people with albinism; whereas in Chapter 13 preventive management, empowerment, advocacy, support services, support groups, and albinism associations will be discussed. The next chapter, Chapter 14, will present the personal perspective and life story of a person with albinism. Lastly, the concluding chapter, 15, will summarize all the key points discussed in the book, make suggestions for research directions, and consider possible future developments in the field, as well as the implications for improving the quality of life for persons with albinism in Africa.

The following sections of this chapter will cover definitions of OCA, clarification of some of the terms used throughout the book, and a broad view of the historical background of the condition, as understood from the available publications and the documented research carried out over past centuries. Because the condition has been observed frequently in Africa, many of the writings and much of the research undertaken on the African continent is presented. However, some research from countries on other continents is also covered (e.g., the extensive work undertaken by Witkop et al. (1983) on African Americans and American Indians and that of Froggatt (1960a) in Northern Ireland). In addition, the informative studies on some isolates, such as the San Blas Indians in Panama (Keeler, 1953), and Hopi Indians in Arizona, United States (Woolf and Grant, 1962), in which high rates of the condition have been found and who were subsequently investigated and reported on in some detail, are discussed.

Some possibly well-known information will be presented in this chapter, while several reports that have been published in rare and/or discontinued journals, as well as some that are little known or have not been published at all, will be included. Various sources have been used, some being ancient, some more modern, some extracted from archival material, and others from unpublished documents available to the writer.

Definitions

In 1971 Witkop defined albinism (somewhat imprecisely) as a “hereditary defect in the metabolism of melanin” resulting in a decrease or absence of this pigment in skin, hair, and eyes. However, in 1983 Witkop et al. recommended that use of the term albinism should be restricted to congenital hypomelanosis that affects only the eyes (OA) or involves both the eye and integument (OCA) and is accompanied by nystagmus, photophobia, and decreased visual acuity. They specified that the terminology used in classifying the different types of albinism should indicate the extent and nature of the pigmentary involvement, wherever possible.

In 1996 Oetting et al. (p. 330) offered a more precise definition: “Albinism represents a group of inherited abnormalities of melanin synthesis. It is characterized by a congenital reduction or absence of melanin pigment in association with specific developmental changes in the optic system resulting from the hypopigmentation.”

In the heterogeneous group of disorders called albinism there are two main categories: the defect impacting either the entire melanocyte system, resulting in broad phenotypic effects (e.g., OCA), or more prominently affecting melanocytes at a specific site with localized phenotypic effects (e.g., OA). The former is generally inherited as an autosomal recessive condition, whereas the latter is usually inherited as an X-linked recessive, although there have been some reports of autosomal recessive inheritance. The present book is concerned only with the former (OCA) and more common category (Fig. 1.1 shows an affected individual and her family).

The term albinism includes a number of inherited disorders that affect pigmentation. The condition was originally thought to be caused by different mutations at one genetic locus, but it is now understood that the genetics of albinism is complex and that there is genetic locus heterogeneity. The nomenclature and classification of the condition are difficult and currently being clarified as new molecular genetic information becomes available. A detailed description of the various forms of albinism is provided in Chapter 5. However, the focus of the book will be on the three common types of albinism (see Oetting and King, 1999), which include OCA1 (previously called tyrosinase-negative, based on the lack of tyrosinase enzyme activity), OCA2 (previously called tyrosinase-positive) and its subtype brown OCA (also called brown albinism or OCA2B), and OCA3 (also called rufous or red albinism or ROCA).

The terms “person with albinism” and “people with albinism” (sometimes abbreviated to PWA) will usually be used in the text because these are the more politically correct (and accepted by those with the condition) and less stigmatized terms, at the time of writing, compared with the other terms used in the past. However, the word “albino” will also be used occasionally, in certain contexts and where the authors of articles under discussion used the term (for a discussion of this issue see the National Organization for Albinism and Hypopigmentation, or NOAH, website). Nomenclature for the indigenous people of Africa is also somewhat problematic. Previously, some authors have used the words Negro (or negro), Negress, or Negroid, but these terms are no longer appropriate nor acceptable in Africa; presently the term Black (or black) is deemed preferable. However, in this book, where necessary, the term used by the author of the article under discussion may be used, but in general the term Black will be applied preferentially. The word White is used preferentially, but Caucasian or Caucasoid are applied where they were used by the original authors, to refer to people of European extraction.

Figure 1.1 An individual with OCA2 and her family. The affected individual has developed a cancerous lesion on her face. Pho...