Noonan Syndrome
Short phrase below the image: What is Noonan syndrome? Everything about the causes and symptoms of this disorder.
Symptoms and Causes
Noonan syndrome is a genetic alteration that causes abnormal physical development affecting certain parts of the body and, in some cases, also impairs cognitive ability. It can manifest to varying degrees depending on the individual, which is why life expectancy varies based on whether or not the heart is severely affected.
Although it is typically inherited in an autosomal dominant pattern (a mutated gene is passed from one parent to the child), many individuals with Noonan syndrome do not have a family history of the disease, meaning the mutation arises spontaneously.
The main characteristics of this syndrome include distinct facial features, short stature, and congenital heart disease.
Symptoms
Depending on the degree of severity and the gene affected, the symptoms of Noonan syndrome can vary significantly. The most notable signs include:
- Wide-set eyes that slant slightly downward
- Strabismus
- Cataracts
- Depressed nasal bridge
- Low-set ears
- High-arched palate
- Pulmonary valve stenosis (narrowing)
- Myocardial thickening
- Cardiac arrhythmias
- Delayed growth and short stature in adulthood
- Pectus excavatum (sunken chest)
- Curved spine
- Bleeding problems
Causes
Noonan syndrome may be caused by mutations in several genes involved in gene expression and protein transcription:
- PTPN11 gene, in most cases
- SOS1 gene
- RAF1 gene
- KRAS gene
- BRAF gene
- SHOC gene
- MEK gene
- MAP2K1 gene
This alteration may be inherited or may occur as a de novo genetic condition, meaning the gene changes spontaneously without being inherited from either parent.
Risk Factors
The main risk factor for Noonan syndrome is having a parent with the condition. In these cases, each child has a 50% chance of inheriting the syndrome.
Complications
Noonan syndrome can impact mental health, leading to low self-esteem and difficulties with social interaction. It may also result in additional physical conditions such as abnormal bleeding, easy bruising, infertility due to undescended testicles, structural heart abnormalities, fluid accumulation, or leukemia.
Prevention
Noonan syndrome cannot be prevented.
Which Specialist Treats Noonan Syndrome?
Diagnosis of Noonan syndrome is carried out by a geneticist, while treatment is managed by psychologists, speech therapists, cardiologists, cardiovascular surgeons, or other specialists depending on the associated conditions that may develop.
From early childhood, physical features may appear that raise clinical suspicion. To confirm a diagnosis of Noonan syndrome, a review of the patient’s family history is conducted, along with a genetic analysis of the PTPN11, SOS1, RAF1, KRAS, BRAF, SHOC, MEK, and MAP2K1 genes to check for alterations compared to normal copies.
A negative result does not rule out the diagnosis. In such cases, the specialist relies on clinical findings to confirm the condition, as some of the genes involved in the development of the syndrome have yet to be identified.
When a risk factor is present, a chorionic villus sampling or amniocentesis may be performed during pregnancy to detect the mutation before birth.
Treatment
There is no cure for Noonan syndrome, so treatment focuses on alleviating symptoms and minimizing complications.
The primary concern is usually managing heart abnormalities to ensure proper cardiac function and improve the disease’s prognosis. Valve replacement or regular monitoring may be necessary.
Psychotherapy and speech therapy sessions help improve cognitive and speech development. Educational adaptations in school are also essential in these cases.
