Harper's Practical Genetic Counselling, Eighth Edition

Angus Clarke

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9781000713008
• Edition: 8
• Topic: Medicine
• Subtopic: Genetics in Medicine

Highly valued across the world by genetic counsellors, medical geneticists and other healthcare professionals, Harper's Practical Genetic Counselling has established itself over previous editions as the essential guide to counselling those at risk from inherited disorders.

Fully revised by its new author Angus Clarke, and with additional input from colleagues, this eighth edition provides indispensable and up-to-date guidance, helping readers to navigate the profusion of new information in this area and the associated psychosocial and ethical considerations and concerns. Maintaining the trusted framework of earlier editions, the update presents the latest information on the use and interpretation of genetic test results, including new genomebased investigations and their application in the genetic counselling process. This book will help both the student and the practitioner, as genetic and genomic investigations become progressively more relevant to all healthcare professionals with the mainstreaming of genetics across the full range of medical practice.

The eighth edition of this best-selling text will continue to be an essential source of reference for trainee and practitioner genetic counsellors and medical geneticists, for clinicians and nurses working in mainstream specialties who increasingly are dealing with the genetic aspects of disease, and for practitioners working in settings where referral to a genetics specialist is not readily available. It also provides invaluable background for other healthcare professionals, counsellors, social scientists, ethicists and genetics laboratory staff.

Part 1

General aspects of genetics and genetic counselling

1Genetics and genetic counselling: An introduction

2Genetic counselling in Mendelian disorders

3Common disorders and genetic counselling

4Chromosome abnormalities

5Genetic and genomic investigations

6Dysmorphology and genetic syndromes

7Carrier testing

8Predictive genetic testing

9Prenatal diagnosis, antenatal screening and reproductive aspects of medical genetics

10Special issues in genetic counselling

11Clinical genetics services

12Treatments and trials for genetic disease

1

Genetics and genetic counselling: An introduction

Preliminary: Genetics in healthcare today

What do we mean by ‘genetic counselling’?

History and development of genetic counselling

Constructing a family tree

Diagnostic information

Genetic risk estimation

Basis of risk estimation

Communication and genetic counselling

Backup to genetic counselling

Support in the context of genetic counselling

Preliminary: Genetics in healthcare today

Scope of genetics in medicine

The context of healthcare is changing rapidly, with genetic aspects of medicine receiving progressively more prominence. Much disease is caused by a complex interaction between a person’s genes and their environment over time. This may be thought of as an interaction between the person’s genes, their environment and their experience, from conception onwards. This perspective broadens the scope of genetics within medicine from disease that is primarily genetic in origin to include much else as well.

A question for this volume is how far the recent development of genetics as a biomedical science plays out in the practice of genetic counselling and clinical genetics. It is apparent that the new high-throughput, genome-wide technologies of microarray and ‘massively parallel’ sequencing have enormously increased the information we can generate about genetic variation across the genome, but the information it yields is still applied one gene at a time. The approach in this edition – which will have to be reassessed for future editions – is that the new technologies provide a much more rapid way of identifying the genetic variant underlying a Mendelian or chromosomal disorder. However, an integrative, whole genome analysis of a patient is not yet available in the clinic. The search for specific genetic variants can be relevant to the selection of appropriate therapies for some patients, but this, again, is usually worked through one variant at a time and not in an integrated, whole genome approach because the working out of gene-gene and gene-environment interactions remains enormously challenging. Research based on this additional, genome-level information is proving enormously fruitful but has not yet reached simple clinical application: its immediate clinical utility is limited.

This book aims to set out a clinical approach to genetic disease that addresses the whole person in their family context. This has long been the aim of clinical genetics services, both clinical genetics and genetic counselling, and it is important that we do not lose sight of this in the flurry and excitement of data generated by the new genome-wide technologies. We need to use the new technologies to answer the old questions more thoroughly and more rapidly but should not be distracted by results with no clear interpretation.

While the new tools generate more and more information, our task remains to help patients and family members make sense of what their genetic analysis means for each as an individual. In addition to the ‘traditional’ patients in the genetic counselling clinic, with clearly inherited disease, genetics services are now also seeing patients who have had genomic investigations yielding additional or unanticipated findings and results of uncertain significance. We must all grow accustomed to investigations generating results that are potentially important despite being unconnected with the problem that triggered the investigation. Clinical genetics services then help patients to understand their results, both what they mean for the patient and what they mean for their relatives. Where there is no certainty, they may need both an explanation of, and support to deal with, the lingering uncertainties.

Far from clinical genetics services becoming outdated as genome-wide testing moves into the medical mainstream, they are becoming appreciated as a powerful resource that enables and supports the appropriate application of the new technologies.

What do we mean by ‘genetic counselling’?

Although many people working in the field of medicine are familiar with the term ‘genetic counselling’ and have some idea what it means, many other professionals and even more patients and families are confused by the term. Closer enquiry among patients and colleagues shows a wide variation in people’s concepts of what the process of genetic counselling actually entails. Some envisage an essentially supportive – even psychotherapeutic – role, akin to that of counselling processes in the social field; others see genetic counselling as primarily concerned with special diagnostic tests in inherited disease; yet others regard it as a complex mathematical process involving the estimation of risk.

All these views of genetic counselling contain a considerable element of truth, but none fully identifies what the overall process of genetic counselling actually involves. Even within the group of professionals for whom genetic counselling is a major activity, there are varied opinions as to its proper role and scope, but in essence it is a composite – hybrid – activity, made up of a series of key elements that individually are very different, but which together constitute a process that is highly distinctive in its character and its ethos.

Previous editions of this book have given various definitions of genetic counselling, but none of them is entirely satisfactory. Two approaches will be used to clarify this: we describe the activities that constitute ‘genetic counselling’ and then refer to a recent and widely cited definition of genetic counselling.

The elements of genetic counselling as practised are as follows:

1.Initially listening to the questions and concerns of the patient or family and establishing a relationship with appropriate empathy.

2.Addressing the diagnostic and clinical aspects, including the gathering of information from the patient and family and the checking and documentation of important clinical information about the patient, and also about family members. This may occur in the process of a ...