Characteristics of Noonan syndrome

Noonan syndrome can affect a person in many different ways.Not everyone with the disorder willshare the same characteristics.

The three most common characteristics of Noonan syndrome are:

  • unusualfacial features
  • short stature ( Short stature )
  • heart defects present at birth ( congenital heart disease )

These are discussed in more detail below.

Unusual features

People with Noonan syndrome may have a characteristic facial appearance, although this isn't always the case.

The following features may become apparent soon after birth:

  • a broad forehead
  • drooping eyelids (ptosis)
  • a wider-than-usual distance between the eyes
  • a short, broad nose
  • low-set ears that are rotated towards the back of the head
  • a small jaw
  • a short neck with excess skin folds
  • a lower-than-usual hairline at the back of the head and neck

Children with Noonan syndromealso have abnormalities that affect the bones of the chest. For example,their chest may stick out or sink in, or they may have an usually wide chest with a large distance between the nipples.

These featuresmay be more obvious in early childhood, but tend to become muchless noticeable inadulthood.

Short stature

Children with Noonan syndromeare usually a normal length at birth. However, at around two years old you may notice that they don't grow as quickly as other children of the same age.

Puberty (when a child begins to mature sexually and physically) typically occurs a few years later than normal andthe expected growth spurt that normally happens during puberty is either reduced or doesnt happen at all.

Medication known ashuman growth hormone can sometimes help children reach a more normal height. Left untreated, the average adult heightfor men with Noonan syndrome is 162.5cm (5ft 3in) and for women is 153cm (5ft).

Heart defects

Mostchildren with Noonan syndrome will have some form of congenital heart disease. This is usually one of the following:

  • pulmonary stenosis where the pulmonary valve (the valve that helps control the flow of blood from the heartto the lungs) is unusually narrow, whichmeans the heart has to work much harder to pump blood into the lungs
  • hypertrophic cardiomyopathy where the muscles of the heart are much larger than they should be, whichcan place a strain on the heart
  • septal defects a hole between two of the chambers of the heart (a "hole in the heart"), which can cause the heart to enlarge and/orlead tohigh pressure in the lungs


Overall, the risk of developing cancer doesnt appear to be much higher than for people without Noonan syndrome, although there may be a very small increased risk of some rare childhood cancers.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 25 Nov 2016