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

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 variants (also known as mutations), which can be inherited (passed down from parent to child). Other conditions that appear to run in families are not caused by variants in single genes. Instead, environmental factors such as dietary habits, pollutants, 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 health 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


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

This condition affects members in each generation of a family.

Three generations of a family with a genetic disorder.
Credit: U.S. National Library of Medicine