Can a genetic blip cause a blood clot?

I get frustrated that the smart scientists don’t know how to easily explain it to me very well. So let me try.

A machine called a gene sequencer processes a single vial of my blood. That machine then reads 3 billion chemical building blocks in my DNA. That sequence is called our genome. It contains our genes that make me ‘me’, and you ‘you’, and a lot more that we won't get into right now.  

When that computer program compared my genomic sequence—the way my genetic building blocks are arranged—to the standard template of any human being, it found roughly five million places where my differed from the norm.

Regardless, I was alarmed.

That number sounds scary until you realize that five million variations isn’t that big a deal. When the machine filtered my five million personal quirks, it only flagged six items that could be a clinical concern. 

Four of those six ‘uh-ohs ’ didn't even matter at all. They indicated I was just a carrier of something, meaning I inherited a mutated gene that would only cause illness if it matched a gene found in both my parents. But without that pair, the gene stays dormant and poses no threat to my health today.

The two remaining genes that could be risk factors for something, my ‘terrible twos,’ laid out the tension between genetic theory and reality.

A genetic sequencing test result just shows your predisposition toward something, not an inevitable outcome. 

In my case, a specific gene, SERPINC1, which governs the production of a protein that puts the brakes on blood clotting, might be concerning.

According to the readout, my version of this protein doesn’t function normally, leaving my blood more prone to clotting than average.

In practical terms, I could experience a higher risk during:

Good warning. Yet I am 73 years old, and I have lived my life to the fullest without ever experiencing a single clotted vein. It’s evidence that tempers the raw DNA data, though I wish I had known about the danger when I was 45.

The second finding parted ways with common sense. My data suggested that I carry a genetic variant linked to a severe childhood intellectual developmental disorder. 

Hmmm. Having spent over seven decades building companies, raising a family, and writing for a living, I felt confident that whatever my personal flaws might be, a developmental disorder was not among them. 

The report was obviously describing something real, but it might be mistaking what that reality means for a man of my age.

As we age, science suggests that the stem cells that generate our blood supply copy themselves billions of times over. 

Occasionally, one of those working cells makes a subtle copy error during replication and multiplies faster than the others. It leaves behind a population of blood cells with the new mutation. 

Between 5% and 25% of people in their 50s and 70s harbor these changes, known as clonal hematopoiesis. Importantly, there’s no known connection between clonal hematopoiesis (blood with a copying error) and childhood illness.

So, it seems the genetic test spotted an alteration in my aging blood cells, miscalculating it as an inherited genetic flaw I had carried since the cradle.

That misinterpretation highlights the limits of genomic testing. These machines read the master instruction manual with precision, but they rarely see what our bodies are actually producing.

However, scientists are now finding that this genetic change could influence cardiovascular health in ways they’re only beginning to comprehend. 

The three stents in my heart seem like a red flag.

I recommend the test for everyone. Just be aware of the limitations.

Ultimately, sequencing when you get older does not deliver conclusive answers or a clear diagnosis. It produces a collection of hypotheses that mean very little until a doctor goes back to the basics and tests the living chemistry of your body. 

In my case, confirming the blood-clotting risk requires an inexpensive lab test.

Though this mountain of data would have offered its greatest practical value to me at 30, when I could have moved the needle faster by adjusting my habits, it is now a postscript to a life lived large.

It’s also given me a useful question to ask my doctor, who is always my final source for what I should worry about.

Read next: The risk of clotting rises with age, and researchers are looking beyond inflammation for an explanation.