How Did I Get Marfan Syndrome With No Family History?

It can be incredibly confusing to be diagnosed with a genetic condition when no one else in your family has it. If you have been diagnosed with Marfan syndrome but your parents, siblings, and grandparents do not have it, you most likely experienced a de novo mutation (spontaneous mutation).

In up to 25% to 30% of people with Marfan syndrome, the condition is not inherited from either parent ^[1]. Instead, the genetic change happens entirely by chance.

What is a De Novo Mutation?

Our bodies are built using instructions found in our genes. Marfan syndrome is caused by a change (mutation) in the FBN1 gene, which tells the body how to make a protein called fibrillin-1 ^[1]. This protein acts like the glue that gives strength and elasticity to your connective tissues, blood vessels, and bones ^[1].

In most cases, an FBN1 mutation is passed down from an affected parent to a child. However, a de novo mutation means the genetic change happened spontaneously. This typically occurs in the sperm or egg cell just before conception, or very shortly after the embryo begins to develop.

When this happens:

• Your parents do not have Marfan syndrome.
• Your parents did not do anything to cause this mutation; it is a natural, random biological event that happens during cell division.
• The chance of your parents having another child with Marfan syndrome is extremely low (usually less than 1%) ^[2].

However, because rare, mild features of the syndrome can sometimes be missed, your care team may still recommend baseline screening—such as an echocardiogram to check the heart and a specialized eye exam—for your parents and existing siblings just to be completely certain ^[2].

Does a Spontaneous Mutation Affect My Prognosis?

Having a spontaneous mutation does not automatically mean your Marfan syndrome will be more (or less) severe than if you had inherited it ^[1]. The severity of the condition and the symptoms you experience vary widely from person to person—even among people with the exact same genetic mutation ^[3]. Your condition will be monitored and managed using the exact same standard of care as anyone else with Marfan syndrome.

What Does This Mean for Your Future?

Even though you are the first person in your family to have Marfan syndrome, the mutation is now part of your DNA. Because Marfan syndrome is an autosomal dominant condition (meaning it affects men and women equally, and you only need one altered copy of the gene to have the syndrome), the inheritance rules change for the next generation ^[1].

This means that whenever you decide to have a child, there is a 50% chance the child will inherit the FBN1 mutation and have Marfan syndrome, and a 50% chance they will not ^[1].

Knowing how your mutation occurred helps you and your care team make informed decisions. Many people with de novo mutations choose to work with a genetic counselor. A genetic counselor can explain your specific mutation and discuss family planning options—such as pre-implantation genetic testing during in-vitro fertilization (IVF)—to help you safely navigate your future ^[2].