What is Noonan Syndrome?

Noonan Syndrome is genetic condition that affects physical and sometimes cognitive development. It can be hereditary but is just as often caused by spontaneous mutations. The DNA changes result in a specific set of physical characteristics such as short stature, congenital heart defects, chest deformities, wide and/or webbed neck, undescended testicles in males, low muscle tone and specific facial characteristics like widely spaced eyes, a cute little turned up nose and folds covering the inside corner of the eyes. In addition to physical changes, there can also be developmental delay.

In medical terms, it's called an autosomal dominant condition. Current estimates have the prevalence to be 1:1000 to 1:2500. Because the disorder has variable expressivity, it is possible that the prevalence is actually much higher however the disorder is often overlooked in adults until their child presents a more severe case. Currently, the average age of diagnosis is 9 years and life expectancy is normal barring severe cardiac complications.[1]

There is a wide range of complications that can accompany Noonan Syndrome - failure to thrive, eating difficulties, mild to severe reflux, and so on and so on...

In all our researching, no one has presented a more concise and readable description of Noonan Syndrome than The Mayo Clinic. It's the link we shared with our families and I encourage you to read and share it. The list of complications is clear and the whole document manageable - not too overwhelming.


1. Allanson, J.E: The Clinical Phenotype of Noonan Syndrome. Noonan Syndrome and Related Disorders. Karger, 2009, vol 17

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