Two men standing in place of DNA connections. An older gentleman is holding up a piece behind a younger man.

Getting MS: Heredity and Genetics

Twenty-some years ago, after waking up with numb legs that I eventually lost all control of, I was whisked into a hospital for a myriad of tests to determine what was wrong with my body. While the doctors were at a loss as to what caused my condition, my family was quick to offer up a suggestion: multiple sclerosis.

What's the deal with genetics and inheritance?

They were quick to make this suggestion because my grandfather also had MS, they’d seen the effects of the disease (he lived with us and my family cared for him), and they were pretty certain what was wrong with me. Despite that, my family's suggestions were ignored because, as the doctor’s said, “MS isn’t something you can inherit.” My family would later prove to be correct when I was officially diagnosed with MS. My situation actually isn’t that uncommon. Numerous families have multiple members who get diagnosed with MS, so what’s the deal with genetics and inheritance when it comes to MS? Let’s take a look!

A family history of MS

I’m very lucky to have a well-researched family with lots of details regarding its previous members. My great-grandmother was a historian, who, as a passion, used her skills to conduct careful research into our family’s history and documented it. Reading through it, it’s pretty clear that there were members of the family that had MS before people knew what MS was. Family members who had trouble walking, or walked with a limp, slurred their speech, had vision problems, etc. It wasn’t until my grandfather was diagnosed that medicine had really come up with a name for it. With all that in mind, it’s understandable that my family was quick to suggest that I too had been befallen by this disease.

MS isn't an inherited condition

Despite my eventual diagnosis, the doctors were still correct, MS isn’t an inherited condition. While my family has a history of people with the disease, there are many that don’t. For every person like me, there are many who are the first and only case in their entire family history. To be considered an inherited disease, it would have to be passed on in a predictable way, and MS simply doesn’t act that way. When a condition is inherited, genes that cause the condition are passed down generation to generation. Children in families with inherited conditions typically have a predictable chance of getting the condition, which doesn’t exist with MS. Along those lines, when it comes to identical twins if a condition can be inherited, either both twins will have it or not have it (as they have identical genes).1 That doesn’t occur when it comes to cases of MS.

But what part do genes play?

So if it’s not hereditary, what gives? Does my family just have bad luck? Not exactly. While MS isn’t an inherited condition, we do know that genes can play a part. Researchers have identified around 200 genes that each contribute a small increase in risk of developing multiple sclerosis.2 So while we don’t inherit the disease, we can inherit genes that increase our risk of MS. That may seem like semantics, but there really is a difference. We inherit a greater susceptibility to getting MS rather than predictably inheriting the condition. Plenty of families may have this greater risk because of their genes but still never have anyone get MS. So while our genes can put us at greater risk, that’s not the only piece of the puzzle

It’s just not that simple

So in my case, despite a long history of people having MS, I did not directly inherit MS from my family. Yes, I inherited a greater risk of getting MS, but other factors had to contribute to me developing the disease. My siblings also inherited this greater risk but (as of this writing) have not developed MS because genes aren’t the only thing at play when it comes to this disease. I hope to explore some of those other potential factors in future installments. Genetics alone are not a cause for MS, but they can increase our susceptibility to the disease. So while the doctors were technically correct twenty years ago, my family was also onto something with regards to our history of MS.

Thanks so much for reading and always feel free to share!

Devin

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