Chapter 10: Human Genetics as a Medical Specialty

Introduction

Human genetics has four important functions in medicine:

  • Diagnosis of genetic disorders through a detailed personal and family history, physical examination, and diagnostic laboratory evaluation
  • Anticipatory guidance and management regarding interdisciplinary care for individuals with genetic conditions
  • Genetic counseling regarding prognosis, recurrence risk, and availability of patient advocacy associations
  • Clinical and laboratory-based research to identify the molecular bases of genetic disorders and disease susceptibility

Human genetics differs from other medical fields because it is not defined clinically as relating to a particular organ system, age, or gender but is instead defined pathophysiologically through specific factors that contribute to the disease. Therefore, an interdisciplinary approach is essential to fully appreciate the intricacies of most genetic disorders.

In past decades the medical geneticist diagnosed, treated, and followed individuals with rare heritable conditions or sporadic developmental disorders. However, as the human genome emerges from obscurity, all physicians must have a workable knowledge of human genetics and genomics because they too will be responsible for the diagnosis and treatment of the “genetic patient.”

Nevertheless, even in the postgenomic era, the human geneticist is presented with the puzzles of medicine and has a key role in the diagnosis and treatment of relatively common and very rare genetic diseases. The components of these puzzles are nothing more than medical history, familial history, physical examination, and synopsis of findings from specialized examinations; yet, it is the clinical geneticist who has the patience, skill, and insight to fit these pieces into the portrait of the final diagnosis.

The challenge for the clinical geneticist is to recognize certain features and patterns found through history and physical examination and to reach a diagnosis, either through recognition of patterns associated with particular syndromes or understanding of the pathophysiology and molecular mechanisms. A detailed and well-structured familial medical history, or pedigree, is extremely important in clinical evaluation and in determining whether or not a disease has a genetic component. Diagnostic workup includes specialized laboratory tests that at times appear technically simple; yet, the correct interpretation and evaluation of these tests demand a high level of expertise.

Establishing a diagnosis is important for the obvious reason of commencing specific therapy; but even for those conditions that are not treatable by specific intervention, the diagnosis is imperative for the medical and psychological health of the patient and family. Determining a diagnosis provides the often overlooked benefits of increasing medical surveillance, enabling individualized education plans, developing knowledge of recurrence risk, and enabling patients to network with disease-specific support organizations.


Important

Establishing an etiological diagnosis:

  • Is crucial for starting specific pharmacological therapy
  • Provides a basis for anticipatory guidance and management of and/or screening for medical, developmental and educational issues
  • Allows the determination of accurate recurrence risks in family members
  • Imparts a tangible psychological benefit for the patient and family who find closure with the knowledge of a diagnosis and identification of condition-specific support groups

Once a diagnosis is made, the geneticist becomes the conductor for the patient’s and often the family’s medical management and care, which can involve specific treatment (e.g., for metabolic disorders), organ system surveillance (e.g., for cancer syndromes), and coordination of interdisciplinary care. The geneticist also plays the role of educator for many rare disorders, educating the patient, family, and interdisciplinary team of physicians and health care providers. Once these tasks are accomplished for any given patient, the geneticist may take a secondary role in the patient’s care.

Genetic counseling is the third important function of the medical geneticist. As mentioned previously, a unique role of the genetic medical specialist is educating the patient and family not only about the medical implications of the diagnosis but also about the educational, social, and reproductive implications. The diagnosis of heritable or developmental conditions carries with it the burden of guilt and uncertainty. While the guilt is not based on scientific fact or even common sense, it is no less real to the individual who harbors it. The uncertainty, however, can be quite real, especially for those rare conditions for which there is little understanding, treatment, or support.

The geneticist, through empathetic communication and knowledgeable resources, is charged with ushering patients through this difficult transition from not knowing a diagnosis to knowing that the diagnosis may have prognostic and reproductive implications. How is the disease inherited? What do the genetic findings signify for the patient and his or her family? What is the significance for the affected individual and his or her relatives? What is the recurrence risk for future pregnancies?

How did the genetic change occur, and is the patient somehow at fault? How does one cope with knowledge of genetic changes and variants? These questions are of vital significance for the patient and the family and require a competent, professional, and empathetic consultation. Because a genetic counseling session is often long and emotionally charged, and covers complicated material, a geneticist often provides a counseling report to the family, which serves as an important reference for them in the future.

One can appreciate that the human geneticist is an investigative physician, effective educator, and empathetic communicator. One can also appreciate that the field of medical genetics and medicine in general would be stagnant if it were not for the efforts of human genetics research in the laboratory, at the bedside, and, most importantly, in translation between those two realms.

Research is necessary to characterize rare and newly identified syndromes as well as to dissect and define the pathophysiological mechanisms of well-established medical conditions such as hypertension, diabetes, and cancer. We are far from a complete understanding of the genetic bases for health and disease, yet each step toward this goal translates to improved diagnostics, therapy, and prevention.