Noonan syndrome

Noonan's genetics are from autosomal dominant inheritance; This means that if one of the parents carries the gene that transmits it, the children have a 50% chance of suffering from the disease. Between 30 and 75% of those affected have relatives with the syndrome. An incidence of 1 in 1,000 to 2,500 newborns is estimated with the same prevalence among men and women.

History of the disease

In 1963, an American pediatrician and cardiologist, described several cases of children with characteristic facial features and short stature. In 1994, the clinical geneticist Jamieson defined alterations in chromosome 12 that all of them shared.

It is in 2001 when alterations are identified at the molecular level, with mutations in the PTPN11 gene that alters the functioning of the protein tyrosine phosphatase.

How it manifests

The most important signs of Noonan syndrome are:

• Delayed growth and short stature.
• Babies with NS at birth are of normal or short weight and height.
• On many occasions the little one has difficulty sucking and rejects some foods due to their texture. They grow slowly but progressively, becoming very evident in adolescence where they do not develop the peak of pubertal growth.
• Bone age is delayed and that means they can grow up to 20 years old.
• In adulthood, the average height reached is 170 cm in men and 153 cm in women.
• heart problems (cardiopathies) in 50-80% of cases. There is usually an associated murmur. The most frequent alterations are the following:
  • Alterations in the pulmonary valve of the heart. This narrows, making it difficult for the blood to circulate properly to the lungs (pulmonary stenosis 50-70% of cases).
  • muscle thickening of the ventricles of the heart that expels blood known as hypertrophic cardiomyopathy. With a frequency of 20-30% of cases.
  • About 60% have the altered one, although apparently the heart is normal.

Almost all of those affected have very characteristic facial features that soften with age. The most characteristic are:

• Increase in the distance between the eyes ()
• Appearance of a skin fold on the inside of the eye (epicantus) reminiscent of an oriental aspect.
• Inclined eyes, the inner part being higher.
• Short and wide neck.
• Ears lower than usual, tilted back and wide nose.
• Hair growth from the upper cervical area.
• Dove-shaped chest”: The chest is bulging in the upper area (Pectus carinatum) and dug inside, in the lower zone (Pectus excavatum). This deformity makes the chest look like that of a bird, which is why this condition is sometimes referred to as "pigeon breast."
• Increased distance between the nipples (75-95%).
• Deviations in column () (15%)

Other less frequent anomalies:

• Mild cognitive deficit. 25% of cases may have learning difficulties. There is motor retardation, they mature more slowly than those of their age. Supportive therapies throughout his childhood improve his evolution.
• Clotting disorders: up to 55% of patients have a greater tendency to bleed. There may be coagulation alterations in 33% of cases, with a deficiency of coagulation factors (VIII, XI and XII), low and / or defective platelets.
• Lymphatic system disorders. Inflammation or deformity can be seen in some parts of the body because lymph accumulates. A transparent fluid in the body that in this syndrome does not circulate well.
• Hearing abnormalities. Hearing loss due to recurrent otitis media is common (15-40%)
• The testicles They are frequently found in the abdomen, because during gestation or pregnancy they have not descended into the scrotal bag. This disorder, called cryptorchidism, is common in men (77%), and can cause low fertility in maturity. Fertility in women is normal.
• Liver-spleen larger than usual.
• At the digestive level: constipation, gastroesophageal reflux, repeated vomiting are also frequent.
• pains articular of unknown origin.

Diagnosis

For many years, the diagnosis of Noonan syndrome has been purely clinical, based on the Signs and symptoms until the appearance of genetic tests.

There are currently molecular diagnostic tests used to detect this syndrome in the form of or by studying the entire genome. PTPN11 molecular study can be performed in case of high clinical suspicion from o. To

The optimal time for determining genetic risk and discussing the availability of prenatal testing is before pregnancy.

During pregnancy we can suspect this syndrome before a excess amniotic fluid in the mother's belly (polyhydramnios), pleural effusion, or a lump of lymph known as a cystic hygroma in the fetus.

Noonan syndrome is sometimes diagnosed as an adult, after having a child with a more obvious condition because the manifestations of the disease can range from mild to more severe.

Treatment

There is no specific treatment. These patients need the intervention of various specialists (cardiology, endocrinology, genetics, etc.) and follow-up by him.

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Growth hormone has been used with success in some people with this syndrome to improve height, muscle tone, cognitive area, and overall physical improvement.

• It is a genetic disease that is typically characterized by typical facial features, short stature, and heart problems.
• Currently there are molecular diagnostic tests used to detect this syndrome in the form of genomic tests or by studying the entire genome.
• There is no specific treatment. These patients need the intervention of various specialists (cardiology, endocrinology, genetics, etc.) and a follow-up by the pediatrician or their family doctor.