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What does it mean if a disorder seems to run in my family?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Inheritance

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

A disorder is considered to "run in a family" when multiple members are affected, which may be due to inherited gene variants, environmental factors, or a combination of both.

Overview

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.

Determining Inheritance

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. They will typically ask about the health of people from several generations, including first-, second-, and third-degree relatives.

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.

When a condition affects members in each generation of a family, it is a key indicator for geneticists to investigate further.

Frequently Asked Questions

Start by listing all first‑degree relatives (parents, siblings, children) and note any diagnoses, age at onset, and treatments. Then add second‑degree relatives (grandparents, aunts, uncles, nieces, nephews) and third‑degree relatives (first cousins). Include dates, severity, and any known genetic tests. A simple spreadsheet or a dedicated family tree app can help keep the information organized and easy to share.
They assess the number of affected relatives, the pattern of inheritance (autosomal dominant, recessive, X‑linked), and whether the disease appears in each generation. If the pattern suggests a single‑gene disorder, they may recommend targeted sequencing or a gene panel. If the pattern is unclear or involves multiple genes, broader tests like whole‑exome or whole‑genome sequencing may be considered.
geneticist will look for a pattern where the condition shows up in multiple generations and in both parents and children. If the disease appears only among people who share the same diet, lifestyle, or exposure, it may be environmental. A clear inheritance pattern usually involves the same gene being passed from parent to child, especially if it shows up in both sexes and across several generations.
Not necessarily. Many inherited disorders have variable penetrance, meaning not everyone who carries the gene will show symptoms. Some conditions also require a second genetic hit or environmental trigger. Genetic counseling can estimate your personal risk based on family history and, if appropriate, genetic testing.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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