Dr. Joseph Sirven: It’s All Relative

By Dr. Joseph Sirven
Published: Friday, October 9, 2015 - 10:29am
Updated: Friday, October 9, 2015 - 10:48am
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Dr. Joseph Sirven
Dr. Joseph Sirven

The future of medicine is all relative now. Our medical commentator Dr. Joseph Sirven explains.

“I went to a lab and had my daughter’s DNA tested for genes associated with epilepsy and … its positive!”  The mother and daughter both broke down in tears. 

“This is not terrible news,” I started. 

“How can you say that?” the mom interrupted. “This means all her children and my grandchildren will be affected. This is a nightmare!”

I looked at both of them.

“No, actually, it isn’t, and just because you have a gene does not mean that everyone down the line will have epilepsy. It doesn’t work that way,” I said.

They both suddenly looked relieved.

As genetic technology becomes accessible and cheaper, researchers are routinely finding genes that could potentially cause many diseases.  Genomic tests are commercially available and patients are getting their chromosomes mapped making my clinical scenario routine.  The problem is that this information can be a psychological powder keg.  Our perspectives on genetic causes of disease are still rooted in the last century with an erroneous belief that inheriting a gene dooms a person and their kids to a certain future.

True, there are certain conditions where inheriting a gene can lead to serious consequences. But, there are far more common conditions in which an identified gene does not necessarily mean you’ll get a disease.

The reason for this is a new understanding of genetics, specifically the interplay between genes and environment known as epigenetics. Every cell has a DNA sequence — the blueprint that distinguishes one person from another. However, transmitted along with one’s DNA is how that DNA is packaged and this is called the epigenome. It turns out this information is just as important as the DNA because it can be modified by the environment and age. 

So, someone might have a gene for cancer and if they are exposed to a certain environmental risk — perhaps they smoke — that gene then gets turned on and the cancer occurs. 

Epigenetics is important because for all common diseases like Alzheimer’s, cancer or heart disease, the chance of getting the disease requires a genetic predisposition and an environmental influence that shapes the risk. The challenge for doctors and researchers is finding ways to both calculate and communicate the risk to a patient. 

This is hard because many disease specific risk factors aren’t yet known and it’s hard to measure an individual’s cumulative environmental exposures.

Regardless, epigenetics is where the future of medicine lies.   

So simply finding a gene linked to a disease doesn’t give the whole story. It’s all relative — just not the way we thought.

Dr. Joseph Sirven is the chairman of neurology at the Mayo Clinic.