Healthcare professionals have long known that common diseases (e.g., heart disease,cancer, and diabetes) and rare diseases (e.g., hemophilia, cystic fibrosis, and sicklecell anemia) can run in families. For example, if one generation of a family has highblood pressure, it is not unusual for the next generation to have similarly high bloodpressure. Family history can be a powerful screening tool and has often been referred toas the best “genetic test.” Family history should be updated on eachvisit, and patients should be made aware of its significance to their health. (SeeAppendix D for the Healthcare Provider Card.)
3.1 Importance of Family History
Family history holds important information about an individual’s past andfuture life. Family history can be used as a diagnostic tool and help guidedecisions about genetic testing for the patient and at-risk family members. If afamily is affected by a disease, an accurate family history will be important toestablish a pattern of transmission. A family history can also identify potentialhealth problems such as heart disease, diabetes, or cancer that an individual may beat increased risk for in the future. Early identification of increased risk mayallow the individual and health professional to take steps to reduce risk byimplementing lifestyle changes, introducing medical interventions, and/or increasingdisease surveillance.
Although providers may be familiar with childhood-onset genetic conditions, manycomplex, adult-onset conditions can also run in families. For example, about 5 to 10percent of all breast cancers are hereditary. These cancers may be caused bymutations in particular genes such as BRCA1 or BRCA2. The U.S. Preventive ServicesTask Force (USPSTF) recommends that doctors and patients be aware of family historypatterns associated with an increased risk for BRCA mutations.
Another example of an adult-onset disease that can be inherited isAlzheimer’s disease. Although most Alzheimer’s disease cases are notseen in many consecutive generations, a small number of cases are hereditary.Hereditary Alzheimer’s disease is an extremely aggressive form of thedisease and typically manifests before the age of 65. Three genes that causeearly-onset Alzheimer’s disease have been identified to-date.
Despite the importance of family history in helping define occurrence of a geneticdisorder within a family, it should be noted that some genetic diseases—suchas single-gene disorders like duch*enne muscular dystrophy and hemophilia A, as wellas most cases of Down syndrome, chromosomal deletion syndromes, and otherchromosomal disorders—are caused by spontaneous mutations. Therefore, agenetic disorder cannot be ruled out in the absence of a family history.
3.2 How to Take a Family Medical History
A basic family history should include three generations. To begin taking a familyhistory, healthcare professionals start by asking the patient about his/her healthhistory and then ask about siblings and parents.
Questions should include:
- 1.
General information such as names and birthdates
- 2.
Family’s origin or racial/ethnic background
- 3.
Health status, including medical conditions and ages at diagnoses
- 4.
Age at death and cause of death of each deceased family member
- 5.
Pregnancy outcomes of the patient and genetically-related relatives
It may be easier to list all the members of the nuclear family first, then go backand ask about the health status of each one. After you have taken the family historyof the patient’s closest relatives, go back one generation at a time and askabout aunts, uncles, grandparents, and first cousins.
3.3 Pedigrees
One can record a family history in several ways, including charts, checklists, forms,and drawings of a family tree or “pedigree.” Pedigrees are sometimesthe preferred method of collecting family history information because a pedigree canbe drawn more quickly than the information can be written and allows patterns ofdisease to emerge as it is drawn. A pedigree represents family members andrelationships using standardized symbols (see Pedigree Symbols below). Because thefamily history continually changes, the pedigree can be updated easily on futurevisits. Patients should be encouraged to record information and update their familyhistories regularly.
The sample pedigree below contains information such as age or date of birth (and ageat death and cause of death for all deceased family members), major medical problems(with age of onset), birth defects, learning problems and mental retardation, andvision or hearing loss at a young age. For family members with known medicalproblems, ask if they smoke, what their diet and exercise habits are, and if theyare overweight.
Selected References
Bennett RL. The Practical Guide to theGenetic Family History. New York: Wiley-Liss, Inc.; 1999.Centers for Disease Control and Prevention. Office of Genomics and DiseasePrevention. Using Family History to Promote Health.www.cdc.gov/genomics/public/famhist.htm.
Genetic Alliance. Taking a FamilyHistory; 2004. www.geneticalliance.org/ws_display.asp?filter=fhh.
March of Dimes–Genetics and YourPractice. www.marchofdimes.com/gyponline/index.bm2.
My Family Health Portraitfamilyhistory.hhs.gov.
U.S. Department of Health and Human Services.U.S. Surgeon General's Family Health Initiative; 2004.www.hhs.gov/familyhistory/
