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Noonan syndrome can affect a person in many different ways. Not everyone with the condition will share the same characteristics.

The 3 most common characteristics of Noonan syndrome are:

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:

Children with Noonan syndrome also 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 features may be more obvious in early childhood, but tend to become much less noticeable in adulthood.

Short stature

Children with Noonan syndrome are usually a normal length at birth. However, at around 2 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 physically and sexually) typically occurs a few years later than normal, and the expected growth spurt that usually happens during puberty is either reduced or doesn’t happen at all.

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

Heart defects

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

Read more about the different types of congenital heart disease.

Other characteristics

Other less common characteristics of Noonan syndrome can include:

A variety of different tumours (cancerous growths) have also been found in people with Noonan syndrome, but it’s often not clear if these are caused by the condition or occur by chance.

Overall, the risk of developing cancer doesn't 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.