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Noonan Syndrome Noonan Syndrome
Noonan syndrome is a fairly common autosomal dominant genetic disorder. An autosomal dominant disorder means that you only need to receive one defective... Noonan Syndrome

by Kimberly Allen RN

Noonan syndrome is a fairly common autosomal dominant genetic disorder.  An autosomal dominant disorder means that you only need to receive one defective gene out of the pair you get from your parents.  There are also cases of Noonan syndrome that develop because of a spontaneous genetic mutation, in other words there is no family history.  Noonan syndrome affects both boys and girls as well as all ethnic groups equally. In the US it is estimated that 1 out of every 2500 children born are born with Noonan syndrome.
There are four different genes that if mutated can cause Noonan syndrome.  In about 50% of the diagnosed cases of Noonan syndrome the mutation occurs in the gene known as PTPNII.  The most severe form of Noonan syndrome occurs when the mutation occur in the KRAS gene which accounts for approximately 5% of the children diagnosed with Noonan syndrome.

Triangulated face, wide-set eyes and low, droopy ears are common characteristics of Noonan’s Syndrome.

All of the genes that can cause Noonan syndrome provide the instructions for the formation of the proteins that are needed for the proper formation of a variety of different tissues during fetal development.  These proteins are also needed for cell division  and movement as well as determining which cells mature to perform specific functions. When there are mutations in any of the four genes that can cause Noonans syndrome, the resulting protein is continually active when it should switch on and off in response to the signals that control fetal growth and development.  It is the continual activation that interferes with the regulation of the systems that control cell growth and division which in turn causes the characteristic features of Noonan syndrome.
Noonan syndrome is considered a developmental disorder that is characterized by short stature, unusual and distinctive physical features like a triangular shaped face, their eyes are usually wide set and slanting downward, the ears are usually lower and there is a deeper groove and wide peaks in their upper lip.  Most also have a lower hairline on the back of their head.  Many children born with Noonan syndrome also have at least one or more congenital heart defects that interfere with the normal function of the heart.  The symptoms of Noonan syndrome can vary in severity from mild to life threatening.
Most cases of Noonan syndrome are diagnosed at birth, however there are mild cases that aren’t diagnosed until the child gets older.  Some cases of Noonan syndrome aren’t diagnosed until a person reaches adulthood and has a child with the more obvious symptoms of the disorder.  The distinct facial features is one of the key clinical findings that leads to a child being diagnosed with Noonan syndrome.  Once the Dr has made a presumptive diagnosis of Noonan syndrome he/she will do further tests including and electrocardiogram and an echocardiogram to determine the severity of the disorder.
Treatment of Noonan syndrome is focused on treating the symptoms and complications that accompany the disorder.  The type and severity of the symptoms determines the type of treatment.  The Dr may prescribe medications to help treat some of the different heart problems and if the heart valves are not functioning your child may need surgery to repair any defects.  Many children with Noonan syndrome also recieve treatment to improve their growth.
Having a child with any illness let alone a genetic disorder that can require extensive medical treatment depending on the severity can bring alot of stress.  There are numerous support groups available for families and children with Noonan syndrome.  Talk with your Dr about a group near you.  Support groups can be a great help and resource for many people.

Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at