Noonan syndrome is a disease affecting different parts of the body. It is characterized by unusual facial features, small build, heart failure, problems with blood circulation, skeletal deformities and other clinical signs.

 People with this disease have distinctive features such as a deep groove between their nose and mouth, an enlarged space between the eyes, tooth misalignment, and a smaller than normal lower jaw.

Children with this syndrome usually have a small neck.

At birth, the individual has a weight and height close to normal. However, the abnormally low level of growth hormones in these patients impairs the development of the patient.

Most people with Noonan syndrome develop heart complications. The most characteristic is the narrowing of the heart valve controlling blood flow from the heart to the lungs. Some also have hypertrophic heart disease, which is an enlargement of the heart muscle.

Male subjects with the disease in adolescence exhibit a delay in the puberty phase. Most of them are also infertile and therefore cannot have children.

Noonan syndrome can cause a significant set of signs and symptoms. Most affected children have normal mental development, however, some may have intellectual disabilities. In addition, eye and hearing problems have already been noted in some cases of the disease.

The development of cancer can be one of the complications visible in this disease. Especially concerning the development of leukemia in patients with circulatory problems.

It is a rare disease, the approximate prevalence of which (number of cases in a given population at a given time) is between 1 / 1 and 000/1 people.

Noonan syndrome is characterized by different symptoms visible in different patients.

The clinical signs most often found are:

– unusual facial features;

– a small build;

– cardiac abnormalities present at birth.

The characteristics of the face are reflected in:

– a broad forehead;

– droopy eyelids;

– an enlarged space between the eyes;

– a large and small nose;

– small cheeks;

– a narrowed neck size.

Children with Noonan syndrome also have abnormalities in the bones that make up the rib cage. This causes the distance between the nipples to widen.

These physical signs can be very present during childhood and then subside in adulthood.

A small build is also characteristic of the disease. At birth, the child presents a normal size. It is around the age of two that development is reduced. This abnormally lower growth in a person’s height is accentuated during puberty.

Auditory manifestations can also be the subject of characteristic signs of the disease, as well as heart attacks. and pulmonary, such as:

– pulmonary stenosis;

– hypertrophic heart disease;

– septal defects (membranes separating the organs).

Finally, other clinical signs may also be common to patients with Noonan syndrome. These include;

– learning disabilities;

– food problems;

– behavioral problems;

– greater risk of bruises and hematomas;

– eye problems;

– hypotonia: deficiency of muscle tone;

– cryptorchidism: testicular abnormalities;

– infertility;

– edemas in the lymphatic vessels;

– problems with the bone marrow.

A large number of tumors can develop as a complication of the disease, especially in children. (2)

The origin of Nooman syndrome is genetic.

Indeed mutations in many genes are the cause of the development of the disease. These mutations may concern the PTPN11 gene, for half of the cases. The SOS1 gene for 10 to 15% of cases and the RAF1 and RIT1 genes for nearly 5% of cases each.

Despite the knowledge of mutations within these genes of interest, there are still cases of the disease, the origin of which is still unknown.

These genes of interest make it possible to give instructions as to the production of proteins involved in the signaling of cell division (proliferation) and thus the development of the body. Mutations within these genes result in an alteration in the production of signaling proteins and lead to abnormalities in the regulation of cell development. (1)

The disease is transmitted in an autosomal dominant fashion. Either, the genes involved in Noonan syndrome are localized at the level of nonsexual chromosomes and the presence of only one of the two copies of the mutated gene is sufficient for the development of the disease.

In this sense, if an individual has one of these two parents with the disease, he has a 50% risk of developing the disease himself.

Prevention and treatment

The primary diagnosis of the disease is differential. It consists of the visualization of atypical symptoms in children. These include:

– distinctive facial features;

– a build smaller than normal around the age of 2 years;

– learning disabilities;

– cryptorchidism;

– edema in the lymphatic vessels.

The second phase of diagnosis is based on genetic testing.

In addition, in most cases, the diagnosis can be confirmed during a blood test.

Other tests also make it possible to confirm or not the presence of the disease. Among these examinations, there are;

– the electrocardiogram (ECG);

– echo-cardiogram;

– eye examinations;

– hearing examinations.

The diagnosis can also be made during pregnancy if the mother and / or father has (have) a family history. In addition, ultrasounds performed during pregnancy can determine the presence of abnormalities, such as, for example, too much amniotic fluid, pleural effusion (the presence of fluid in the membrane covering the lungs) or a size abnormally elevated parts of the fetal body. (2)

There is no single treatment for the disease, but a combination of treatments is often necessary to treat a range of symptoms.

For the treatment of the developmental impairment of the child, it is usually put in place between 4 and 5 years until the end of its growth. The prescription of somatropin is most often associated.

As part of language and eating problems resulting from muscle weakness in the mouth. Consulting a specialist doctor is recommended. In the most severe cases, that is to say in infants not knowing how to feed at all, feeding is effective by catheter for a few months.

Surgical interventions correct for testicular abnormalities (cryptorchidism).

Regarding learning difficulties, which concern certain cases of the disease, these can be overcome with the help of specialists accompanying the child in his school career. (2)