Can You Have CMT Without A Family History? Understanding Recessive Inheritance & De Novo Mutations

“How Can I Have CMT If No One Else in My Family Has It?” This is a question I hear often from people newly diagnosed with Charcot-Marie-Tooth disease (CMT). While it’s not directly related to orthotics, it comes up so frequently that it’s worth addressing here.

Most people I meet have just been referred for AFOs (ankle-foot orthoses) after receiving a CMT diagnosis. Naturally, they go home, search for information, and quickly discover that CMT is a hereditary condition. That discovery can lead to confusion—especially when there’s no known history of CMT in the family.

So how is it possible to have a hereditary neuropathy when neither parent, nor any relatives, seem to have it?

The answer lies in how genetic mutations can be passed down—or sometimes, how they arise spontaneously.

Two Ways to Have CMT Without a Family History

There are actually two ways you can be diagnosed with CMT even if no one else in your family has ever had it:

1. Recessive Inheritance

Some forms of CMT are inherited in a recessive manner. In fact, all of the CMT Type 4s are inherited this way. This means that both parents are carriers of the gene mutation, but they don’t show any symptoms themselves. You only develop CMT if you inherit two copies of the faulty gene—one from each parent.

For example, CMT4A is caused by mutations in a gene on chromosome 8 responsible for producing GDAP1, a protein that helps transmit signals along peripheral nerves. If both parents pass on this mutated gene, the child will develop CMT. This form tends to be more severe, with early onset and potential complications like vocal cord weakness.

2. De Novo Mutation

In other cases, CMT is caused by a de novo (new) mutation, which means the mutation didn’t come from your parents at all. Instead, it occurred spontaneously in either the sperm or egg before you were conceived.

A 1996 study found that up to 10% of CMT1A cases may be the result of de novo mutations. This is often surprising to patients, but in my experience, it’s not uncommon.

What This Means for You

If you’ve had genetic testing that confirms a CMT diagnosis but no one else in your family seems to have it, chances are you either:

• Inherited a recessive type of CMT, or
• Have a de novo mutation that occurred spontaneously.

In either case, your diagnosis is valid—and you’re not alone. The genetics of CMT are complex, and we continue to learn more with each passing year.If you’re experiencing difficulties with walking, balance, or mobility, the right orthotic support can make a significant difference. Learn more about options at CMTMobilityRescue.com.