Noonan Syndrome

Summery and description

What is Noonan Syndrome?

This is an autosomal developmental disorder that effects a variety of areas of the body. Noonan syndrome can be inherited from one's parents and is caused by a mutation in one of the four identified autosomal dominant genes. This means that it takes just one defective gene from one parent to give a child Noonan syndrome.

Characteristics of this disorder

There are a number of different characteristics that can be present in a person with Noonan syndrome and vary among all individuals with this disorder. Some of the possible characteristics include:

  • Short stature
  • Heart defects
  • Distintive facial features (deep philtrum, widely spaced eyes that are light in color, high-arched palate, small mandible, poor alignment of teeth)
  • Webbed skin on the neck
  • Bleeding problem (trouble clotting)
  • Hearing impairment
  • Possible infertility in males
  • Malformation of rib bones
  • Developmental delays
  • Intellectual disabilities (often mild and with 10-40% needing some degree of special education services)

These characteristics vary in severity from mild to severe depending on the individual and not everyone presents with all characteristics.

Noonan Syndrome. (2011, March 23). Retrieved April 19, 2015, from

Diagnostic criteria

Identification of the clinical signs and symptoms of this disorder may lead a physician to suspect Noonan syndrome. Blood and genetic testing are used to detect gene mutations and confirm the diagnosis of this disorder.

Symptoms of Noonan syndrome can be so mild that they go undetected until adolescence. In this case, blood and genetic testing are needed to confirm the disorder.

Noonan Syndrome. (2013, March 10). Retrieved April 10, 2015, from

Prevalence data

This disorder effects between approximately 1 in 1,000 to 1 in 2,500 people in the US. It can be inherited or can be a result of a spontaneous gene mutation.

Noonan Syndrome at a Glance. (2015, January 1). Retrieved April 10, 2015, from

What don't we know?

It is known that there are four different genes that are associated with 85-90% of Noonan syndrome cases. However, it is unknown what causes the remaining 10-15% of cases.