You’ve heard the saying: It runs in the family. What does this really mean? Biologically-related family members share genes in common, and we can see evidence of this in the physical resemblances among many family members.
Family members also share their environment, dietary and exercise habits, lifestyle behaviors, and cultural practices. Most common health problems are a result of our genes interacting with the environment to cause disease. Chronic health conditions like heart disease, diabetes, mental illness and certain cancers often have a familial component. In families where multiple closely-related biological family members have the same condition, there may be an increased risk for others to develop the same disease.
How do sperm banks evaluate their donor family histories? Genetic counselors work with sperm banks to screen donor family medical histories for risk that exceeds general population risk.
It’s always something
Nearly every family has health conditions that affect its members with increased or decreased frequency. For example, a person in one family may be at greater than population risk for coronary artery disease, while being at lower than population risk for colon cancer. These risks are marginally increased or decreased from the background risk for all families, and all families have some risk.
Compared with common health conditions that have complex causes, some genetic disorders occur with increased frequency in specific ethnic groups and are due to single-gene defects. You are more likely to be a carrier for cystic fibrosis, sickle cell disease, or Tay-Sachs disease if you are a member of certain ethnic groups. Carrier testing is available for many of these conditions.
Just the facts, please
Family medical history is reliable only when the information supplied is accurate and up-to-date. Information should include the name of the disease or condition, the family member who is affected, the age at diagnosis, and for those family members who are no longer alive, how old were they when they died and what was the cause of death? Old age and natural causes are not sufficient explanations for a death.
Watch out for red flags in the trees
Health problems are unlikely to be strongly genetic if they affect people in very old age, or if they are related to exposures such as heavy smoking or exposure to infectious agents or trauma. Conversely, expert examination of the family medical tree can reveal clues that increase the likelihood that a health condition may be hereditary. These red flags include:
- Multiple family members with the same or related disorders
- Earlier age of onset than typical
- Conditions associated with intellectual impairment or developmental delay
- Diagnosis in the less-commonly-affected sex
- Bilateral disease (e.g., breast cancer in both breasts)
- Conditions associated with one or more major birth defect
- Disease in the absence of risk factors or after preventive measures
- Growth abnormalities (asymmetry, under- or overgrowth)
- Consanguinity (parents related by blood)
Until the day comes when genetic screening is cheap and accurate, nothing beats taking a good hard look at the family tree!
Photo credit: flickr