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What does it mean if a disorder seems to run in my family?

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A particular disorder might be described as “running in a family” if more than one person in the family has the condition. Some disorders that affect multiple family members are caused by gene mutations, which can be inherited (passed down from parent to child). Other conditions that appear to run in families are not caused by mutations in single genes. Instead, environmental factors such as dietary habits or a combination of genetic and environmental factors are responsible for these disorders.

It is not always easy to determine whether a condition in a family is inherited. A genetics professional can use a person’s family history (a record of health information about a person’s immediate and extended family) to help determine whether a disorder has a genetic component. He or she will ask about the health of people from several generations of the family, usually first-, second-, and third-degree relatives.

Degrees of relationship
Degrees of relationship Examples
First-degree relatives Parents, children, brothers, and sisters
Second-degree relatives Grandparents, aunts and uncles, nieces and nephews, and grandchildren
Third-degree relatives First cousins
A condition can affect several generations of a family.

Some disorders are seen in more than one generation of a family.

For general information about disorders that run in families:

Genetics Home Reference provides consumer-friendly summaries of genetic conditions. Each summary includes a brief description of the condition, an explanation of its genetic cause, and information about the condition’s frequency and pattern of inheritance.

The Genetic Science Learning Center at the University of Utah offers an interactive discussion of what it means to be at riskThis link leads to a site outside Genetics Home Reference. for disorders that run in families.

The National Human Genome Research Institute offers a brief fact sheet called Frequently Asked Questions About Genetic DisordersThis link leads to a site outside Genetics Home Reference..

The Centre for Genetics Education provides an overview of genetic conditionsThis link leads to a site outside Genetics Home Reference..

The Department of Energy offers a fact sheet called Genetic Disease Information—Pronto!This link leads to a site outside Genetics Home Reference.

Next: Why is it important to know my family medical history?

Published: January 23, 2009