Pediatric Annals

GENETIC SCREENING 

The Family History as a Screening Tool

Jennifer B Stroop, MS

Abstract

Because of the significant impact [that] genetic susceptibility information may have on disease management and prevention, it is vitally important that the public, health professionals and administrators become educated regarding the importance of the family history as a tool for assessing genetic susceptibilities for chronic disease.1

Abstract

Because of the significant impact [that] genetic susceptibility information may have on disease management and prevention, it is vitally important that the public, health professionals and administrators become educated regarding the importance of the family history as a tool for assessing genetic susceptibilities for chronic disease.1

The process of genetic risk assessment will become a routine practice for pediatricians in the coming century.2 Francis Collins, director of the National Human Genome Research Institute, described how "... more and more, patients are bringing the magazine or newspaper into the health care provider's office wanting to know if they are genetically prone to a given disease."3 Many primary care physicians may require further training and information to feel fully prepared for their expanding role in genetics.2

Taking a thorough but concise family history incorporates many of the most important principles of genetics, and is a skill that can be practiced by a variety of medical personnel. This article reviews how to use the family history as an initial screening tool and how to identify patients who may need further genetic evaluation and testing.

SCREENING

The purpose of screening is to identify asymptomatic individuals at risk for disease, with the hope of preventing significant morbidity and mortality.4 Screening is becoming increasingly more important as physicians and health maintenance organizations incorporate strategies of preventive medicine. Genetics is uniquely suited to preventive medicine because patients are considered within the context of their family. One patient's diagnosis may often indicate screening for other family members.

There are many different types of genetic screening. Laboratory methods may include biochemical and physiological analysis, DNA testing, newborn screening, and protein truncation tests.1 The family history is a cost-effective, noninvasive tool for initial genetic risk assessment.5 It can be performed by the physician, by support staff, or even initially by the patient.

The concept of discussing genetics with patients may seem to be mutually exclusive within the context of increasing time constraints.6 A good family history, however, does not need to take a great deal of time. Accurate risk assessment can also save time by avoiding unnecessary tests and procedures. Determining that a condition is not genetic is just as valuable as a possible diagnosis.7 Not only are there medical benefits to taking a family history, but the process also builds patient rapport. Discussion of a familial condition provides an insight into family issues and deeply felt beliefs regarding the burden and cause of a particular disease.8

Table

TABLEWhat to Ask About When Taking a Family History, and Why

TABLE

What to Ask About When Taking a Family History, and Why

WHAT IS INCLUDED IN A FAMILY HISTORY?

Whereas geneticists and counselors prefer a pedigree analysis for a full evaluation, pediatricians in everyday practice may prefer to use a brief series of questions as a screening tool. If the screening yields specific concerns, a pedigree may be useful to gather more detailed information.

Taking a family history starts with general questions (ie, learning problems, pregnancy losses, childhood death, and birth defects). A noted disease or concern is then followed with questions targeted for a specific condition. Patients at risk for genetic disorders can be further evaluated through genetic testing and counseling. When asking patients about their family history, it is. important to give them guidelines about the type of information desired. "Tell me about your family history" may mean the immediate family to some patients and a third cousin once-removed to others. It may be helpful to say, "I'm going to ask you about different medical conditions in your family history. Think about your children, your brothers, sisters, and their children, and your grandparents. I'm also asking about your partner's side of the family." The interviewer can then run through a brief series of conditions, using descriptive terms instead of technical jargon. A patient may remember a cousin in a wheelchair, but he or she may not respond to a "history of myopathy or neuromuscular disorders."

There are some basic disease categories to address when taking a family history (Table). Variations of this list can be expanded into a checklist that is given to the patient prior to the appointment. This allows the patient time to mink about his or her history and to contact other relatives who may provide more detailed information. Reviewing the checklist at the time of the appointment takes a matter of minutes, provides initial genetic screening, and helps to establish rapport.

Asking a series of questions is appropriate for an initial screening tool. A detailed pedigree analysis, however, will provide more information and should be performed when a genetic condition is suspected or has been diagnosed. The following are some basic tips for taking a pedigree5:

1. Record three generations - the child, the child's parents, aunts, uncles, and cousins, and the child's grandparents.

2. Include both sides of the family.

3. Include both affected and nonaffected relatives.

4. If an adult does not have children, distinguish between choice and infertility.

5. Record ages and causes of death.

6. Record primary cancer sites and age of onset for suspected familial cancers.

7. Obtain medical records for family members with a relevant diagnosis.

Those interested in updating their pedigree skills should refer to The Practical Guide to the Genetic Family History.5 This book provides concise instructions about how to draw a pedigree with standardized symbols and nomenclature. Perhaps the most helpful chapter lists directed medical questions for various genetic disorders.

RECOGNIZING PATTERNS OF INHERITANCE5,7

Autosomal Dominant Inheritance

Autosomal dominant conditions are the result of a single altered gene that causes disease. In many cases, there may be an affected person in each generation; males and females are affected equally.

Confounding Factors. There may not be a family history of the condition. Dominant mutations can occur sporadically (sometimes called "new dominant" mutations).

Nonpenetrance refers to a person who has the altered gene but may not express clinical symptoms. For example, if a male has a BRCAl mutation, he is unlikely to have breast cancer. His daughters, however, still have a 50% chance of inheriting the altered gene and the increased susceptibility for breast and ovarian cancer.

Finally, there is the phenomenon of gonadal mosaicism. In certain diseases, such as osteogenesis imperfecta, neither parent is affected and the pedigree seems to indicate a new mutation. There is still a chance that one of the parents carries the mutation in a percentage of the egg or sperm cells, raising the risk of recurrence above that of the general population.

Autosomal Recessive Inheritance

Autosomal recessive conditions are caused by two affected genes; one altered gene is inherited from each parent. There is rarely a recent family history, unless there is consanguinity. Males and females are equally affected. Many inborn errors of metabolism are autosomal recessive.

X-Linked. X-linked recessive conditions are caused by altered genes on the X chromosome. Almost all of those affected are males; females are typically carriers. A few females can have symptoms because of skewed X inactivation. Fathers cannot pass the affected genes to their sons; all of the daughters of an affected man are obligate carriers.

X-Linked Dominant Conditions. Women are usually affected by these conditions. There may be multiple losses and few male siblings because of male lethality.

Multifactorial Inheritance

Many birth defects are attributed to multifactorial inheritance. Multifactorial conditions are thought to be caused by a combination of genetic and environmental factors. A person may be described as inheriting a predisposition to a condition or having an increased susceptibility relative to the risk of the general population. Factors that may also play a role include gender, the degree of relationship to the affected person, and the severity of the defect.

Mitochondrial Inheritance

Mitochondrial inheritance is usually passed on only through the mother, because only the maternal mitochondrial DNA is inherited. However, not all mitochondrial diseases follow mitochondrial inheritance patterns. There are nuclear mutations, often inherited in an autosomal recessive pattern, that can cause mitochondrial disease. Mitochondrial symptoms often involve disorders of the central nervous system. There is an extreme amount of variable expressivity in mitochondrial diseases; age of onset varies from infancy to adulthood. Some conditions are degenerative.

Contiguous Gene Syndromes

Contiguous gene syndromes are caused by submicroscopic deletions or duplications of multiple genes that are aligned together at a specific locus. Contiguous gene syndromes often have a wide range of symptoms, depending on the size of the mutation. There may be a combination of features, including mental retardation, dysmorphic features, and congenital anomalies. The family history is usually noncontributory.

SOME RED FLAGS TO LOOK FOR IN A FAMILY HISTORY

Fatty acid oxidation disorders can be mistaken for Reye's syndrome or sudden infant death syndrome.9 Chromosome problems or syndromes may be indicated by multiple congenital anomalies, mental retardation, or both. Developmental delays with dysmorphic features, birth defects, or other medical conditions are also significant. These concerns are not an exhaustive list for interpreting a family history. As always, consulting an expert is a good rule of thumb when questions remain.

CONCLUSION

A family history has been a standard part the initial patient interview for years.8 A more detailed and targeted family history is helpful when evaluating an established patient for a possible genetic condition. Our rapidly advancing technology continues to create new tests, new questions, and new roles for geneticists, pediatricians, and patients. If a patient brings Internet printouts to the physician's office and asks whether he or she should be tested for a condition, a family history is a good place to start.

REFERENCES

1. Scheuner MT, Wang SJ, Raffel LJ, Larabell SK, Rotter JI. Family history: a comprehensive genetic risk assessment method for the chronic conditions of adulthood. Am J Med Genet. 1997;71:315-324.

2. Fetters MD, Doukas DJ, Phan KLD. Family physicians' perspectives on genetics and the human genome project. Clin Genet 1999;56:28-34.

3. Touchette N, Holtzman NA, Davis JG, Feetham S. Toward the 21st Century: Incorporating Genetics into Primary Health Care. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press; 1997:7-11.

4. Nielsen C, Lang RS. Principles of screening. Med Clin North Am. 1999;83:1324-1337.

5. Bennett RL. The Practical Guide to the Genetic Family History. New York: Wiley-Liss; 1999:1-12, 39-67.

6. St Peter RF, Reed MC, Kemper P, Blumenthal D. Changes in the scope of care provided by primary care physicians. N Engl J Med. 1999;341:1980-1985.

7. Robinson A, Linden MG. Clinical Genetics Handbook, 2nd ed. Boston: Blackwell Scientific Publications; 1993:3-10.

8. Pyeritz RE. Family history and genetic risk factors: forward to the future. ]AMA. 1997;278:1284-1285.

9. Stanley CA, Hale DE. Genetic disorders of mitochondrial fatty acid oxidation. Curr Opin Pediatr. 1994;6:476-481.

TABLE

What to Ask About When Taking a Family History, and Why

10.3928/0090-4481-20000501-06

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