Noonan Syndrome: Symptoms & Signs

Medically Reviewed on 2/7/2020

Noonan syndrome is a disorder characterized by birth defects such as multiple unusual facial characteristics, short stature, heart defects, bleeding problems, developmental delays, and abnormalities of the bones of the rib cage.

Signs and symptoms include the birth defects described above. Abnormal facial features are prominent signs of Noonan syndrome. Additional associated signs and symptoms of the condition can include

  • a broad or webbed neck,
  • eye problems including strabismus,
  • an unusual chest shape, and
  • low- and wide-set nipples.

Males may show undescended testes (cryptorchidism).

Cause of Noonan syndrome

A genetic mutation inherited from a parent or acquired at conception causes Noonan syndrome. Genes involved in Noonan syndrome include PTPN11, SOS1, RAF1, and KRAS.

Other noonan syndrome symptoms and signs

  • A Broad or Webbed Neck
  • Abnormalities of the Bones of the Rib Cage
  • Bleeding Problems
  • Developmental Delays
  • Eye Problems Including Strabismus
  • Heart Defects
  • Low- and Wide-Set Nipples
  • Multiple Unusual Facial Characteristics
  • Short Stature
  • An Unusual Chest Shape

Subscribe to MedicineNet's Children's Health & Parenting Newsletter

By clicking "Submit," I agree to the MedicineNet Terms and Conditions and Privacy Policy. I also agree to receive emails from MedicineNet and I understand that I may opt out of MedicineNet subscriptions at any time.

Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.