Genetic medicine at the bedside

Heredity and Hope: The Case for Genetic Screening

Harvard University Press: 2008. 270 pp. $27.95, £18.959780674024243 | ISBN: 978-0-6740-2424-3

Despite the fresh veneer of technology, medical genetics still follows the old-fashioned practice of medicine. It remains the most clinical of disciplines — in the literal sense, from the Greek klinikos, meaning 'of a bed' — in that most of the genetic physician's work is done at the bedside.

The story of the patient's illness, their family history and the physical examination remain the cornerstones of diagnosis. A clinician must examine the whole body to catalogue subtle and obvious signs and symptoms: the texture of the skin, how the ears are slung, the shape of the uvula in the back of the throat. Clinical findings then cohere, much like stars in constellations, into the eponymous syndromes with which we are familiar.

In Heredity and Hope, technology sociologist and historian Ruth Schwartz Cowan writes brief histories of several hereditary diseases and the scientists and clinicians who developed screening tests for them. Of the thousands of genetic diseases, Cowan focuses on a handful that are atypical in that they are well understood biochemically, genetically and sociologically. These include Tay–Sachs disease and phenylketonuria, which result from enzyme deficiencies, and sickle-cell anaemia and β-thalassaemia, which arise from defects in β-haemoglobin, one of the most studied of all proteins. For each disease, the probability of clinical expression given a specific genotype is very high, making predictions reliable and early detection routine.

Before being implanted in the womb, human embryos fertilized in the lab are genetically tested. Credit: P. GOETGHELUCK/SCIENCE PHOTO LIBRARY

The consequences of these diseases remain devastating to patients and their families. This is especially true in the case of phenylketonuria, where a delayed diagnosis may result in irreversible brain damage. Physicians, parents, patients and insurance providers all agree on the benefits of identifying carriers of the mutant genes or diagnosing disease either in utero or at the time of birth, and identification protocols have been crafted that are acceptable to most. The greatest disagreements centre on what action to take once we have this genetic information.

The author's brief history of eugenics presses the point that medical genetics owes no apologies to society. There is no overlap between those who care for patients with genetic disease and anyone who has advocated the purification of the general germplasm through genetic isolation, including sterilization. This is obvious given that eugenics as public policy and as science met its deserved end in the first half of the twentieth century, whereas medical genetics as a sub-speciality formally began in the 1950s when Victor McKusick opened the Moore Clinic at the Johns Hopkins Hospital in Baltimore, Maryland.

That medical genetics and eugenics sprang from the same scientific soil has given ground to a small chorus of opponents to genetic screening. Trying to pull the ugly thread of eugenics through the fabric of genetics to discredit it, these opponents range from what Cowan calls 'reproductive feminists' to advocates of rights for people with disabilities, and span both the political left and right. This is not to dismiss the defensible reasons to object to population-based screening for specific diseases.

Clinical variability can be huge, even for specific genotypes, so the decision to establish a screening programme is not straightforward. Every medical geneticist has been confronted by the fluid meaning of disability. Despite clear clinical challenges, many deaf people, for example, do not consider themselves disabled and rightly resent being defined by their trait. Medical geneticists have had to adapt to patients' views of themselves.

To justify morally the genetic-screening programmes she writes about, Cowan cites the good intentions of the parties involved, primarily their efforts to relieve suffering. This criterion does not pass philosophical muster, nor is it sufficient to sway vehement opponents. Although her analysis is cursory, it does get to the heart of the matter: hereditary diseases cause great human suffering and everyone wants to help.

What no commentator on medical genetics acknowledges is the hidden sadness, customarily buried, that each geneticist feels when discussing with patients and parents the options for treatment, which are generally few and unsatisfactory. This takes its toll on everyone, although patients always astound with their resilience.

The hard truth is that genetics does not offer easy answers. There are many genetic diseases, and each one is unique. The simplicity of DNA is illusory — our DNA is popularly regarded as our medical fate, but DNA interrogations more often yield notions of risk that have different meanings to patients and physicians. Physicians rarely know the true cause of our complaints. In those genetic cases where simplicity prevails, the testing technology is likely to be adopted. As law in the United States, the Genetics Information Non-discrimination Act may relieve some anxiety about the misuse of genetic information. If only it were so simple to dispatch misery.

Modern healers may claim science to be the foundation of their work, but the key is, in fact, persuasion: to heed advice, to push and persevere, to hope. As the genome is further dissected and better understood, no family of diseases warrants more genuine hope for successful management than genetic conditions. Cowan understands that we must all share that hope for the campaign to be successful.

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Rienhoff Jr, H. Genetic medicine at the bedside. Nature 453, 452–453 (2008) doi:10.1038/453452a

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