Genetic Predisposition: What It Is, What It Means for You

Genetic predisposition is an increased chance that you’ll develop a certain disease based on your genetic makeup. This can be identified via your family history and/or genetic alterations. A predisposition contributes to the development of disease but doesn’t actually cause it.

A genetic predisposition (or genetic susceptibility) isn’t the same as a genetic disease; it’s simply an indicator that, under the right conditions, you’re more likely to develop a disease. It typically takes at least one more contributing factor, beyond the predisposition, to trigger a disease you're susceptible to.

Genetic testing can reveal a predisposition for some diseases, and that can lead some people to take preventive measures so they’re less likely to come down with the illness. Your ability to do that depends on what you're predisposed to and what healthcare providers know about the disease and how to prevent it.

Conditions With Predispositions

A huge number of diseases involve known or suspected genetic predispositions, including some of the most prevalent diseases in the U.S. Some of them are:

• Type 2 diabetes
• Heart disease
• Cancer
• Asthma
• Obesity
• Addiction
• Autism
• Stroke
• Multiple types of mental illness, including schizophrenia and bipolar disorder
• Celiac disease
• Fibromyalgia
• Myalgic encephalomyelitis/chronic fatigue syndrome
• Irritable bowel syndrome
• Autoimmune disease, including lupus, rheumatoid arthritis, and multiple sclerosis

Hundreds of other diseases are known or believed to involve genetic predisposition as well, and researchers are likely to discover even more.

How Predisposition Works

Genetic predisposition comes from genetic variations that are passed down from parent to child. These variations are somehow different from what’s considered the “standard” gene that most people have, and they leave you vulnerable to disease if you encounter the right set of contributing factors at some point in your life.

Contributing factors can be any number of things, including:

• Other genes
• Acute illnesses, like those caused by a virus or bacterium
• Environmental exposures, like pollution or pesticides
• Smoking or other tobacco use
• Alcohol or drug abuse
• Hormonal changes, such as having a baby or going through menopause
• Surgery
• Long-term sleep deprivation

When it takes multiple factors in combination to trigger disease, it’s called a “multifactorial illness.”

Example: Three Siblings

Here’s an example of how genetic predisposition and multifactorial illness can work:

Say “gene A” deals with a protein that’s important to your immune system. It works a certain way in 98% of people, but the other 2% have a variation that makes them deficient in that protein, which makes you extra susceptible to autoimmune disease, like lupus or rheumatoid arthritis.

Imagine you and your two siblings all inherit that variation from your mother. Mom is fine until she enters menopause, at which time she develops lupus.

Sibling one, as an adult, travels around the world and catches a rare viral illness, and instead of recovering normally, ends up with lupus, just like mom.

Sibling two works in an industrial facility and is exposed to some toxic substances that are hard on the immune system. They don’t ever have a major acute illness like sibling one, but they do eventually develop rheumatoid arthritis.

Meanwhile, you manage to go through your entire life without any immune-related problems. You got lucky and never encountered the right combination of contributing factors.

Predisposition vs. Inherited Disease

Having a genetic predisposition to a disease isn’t the same as having a directly inherited genetic disease:

• A genetic predisposition doesn’t guarantee you will develop the disease, it just means you’re more likely to.
• With a genetic disease, if you have the gene(s), you do or will have the disease.

Some inherited diseases require only one parent to contribute the gene for the disease, while some require both parents to contribute one.

Some inherited diseases include:

• Cystic fibrosis
• Fragile X syndrome
• Hemochromatosis
• Huntington’s disease
• Marfan syndrome
• Phenylketonuria
• Polycystic kidney disease
• Tay-Sachs disease

It's becoming more common for people who have known genetic diseases in their family to have genetic testing before having a child so they know their risk of passing along the disease.

Genetic Testing

For some conditions with known predispositions, such as breast cancer, you can have genetic testing to help identify your risk of developing the disease. Knowing your risk may help you make decisions that can keep you healthy.

Genetic testing involves taking DNA from your cells and studying it for specific genes, chromosomes, proteins, and mutations that are known to be involved in certain illnesses. DNA can be acquired from your blood, hair, urine, saliva, bone, or other tissues. It's often collected through a simple cheek swab.

Along with identifying your personal risk and possibly helping with prevention, a genetic test can sometimes help your healthcare provider make a diagnosis or select the best treatment, as well. Genetic testing can:

• Confirm or rule out whether you have a genetic disorder
• Identify your risk of developing or passing on a genetic disorder
• Assess which drug may be most effective for you
• Identify your genetic lineage

Is Prevention Possible?

If genetic testing reveals you have a predisposition to something, or if you suspect a predisposition because of something that runs in your family, it’s natural to wonder if you can take steps to prevent the disease in yourself or your child.

For example, genetic testing for breast cancer predisoposition has led some people to have preventive mastectomies (breast removal). If you’re susceptible to coronary artery disease, dietary changes may be in order.

However, the means of prevention vary greatly depending on what disease you’re predisposed to. Your best option is to talk to your healthcare provider about what your predisposition means for your overall risk and what you may be able to do to mitigate that risk.