Medical Q&As

Noonan syndrome - what is it?

Tell me about Noonan Syndrome.

Noonan syndrome is a rare congenital disorder that is characterised by distinctive facial features associated with abnormalities of the pulmonary valve in the heart. Many of these children suffer from mild mental retardation. Some affected children also have skeletal abnormalities including scoliosis and abnormalities of the breastbone. Most children with Noonan syndrome are of short stature. Additional abnormalities may include platelet and clotting deficiencies. The syndrome is usually inherited as an autosomal dominant trait, which means that there is a 50% chance that it will be inherited on each pregnancy. This also means that the parent transmitting the abnormal gene also has Noonan syndrome but is so mildly affected that they are unaware of that fact. It can also occur as a result of spontaneous genetic mutation. I have never encountered the syndrome in clinical practice here in Ireland and given the incidence of the problem and the size of the Irish population it is unlikely that many Irish doctors will have encountered the syndrome. An American support group has been established and they can be contacted at: