Noonan Syndrome

Noonan Syndrome is a hereditary disorder that hinders the normal body development. It involves rare heart defects, short stature, facial characteristics, slowed growth, bleeding problems, rib cage and bone malfunctions.  Genetic mutation generates this disorder, and a baby inherits it from the parent’s affected gene (dominant inheritance). It may also occur without any family history (spontaneous mutation). Four genes SOS1, PTPN11, RAF1, and KRAS, get altered and are identified to check the disorder till date. This rare condition is seen in about 1 out of 1000-2500 people.

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Noonan Syndrome Causes

Genetic mutation is the primary cause of this disorder and it occurs in multiple genes. Defected genes provoke the protein production which is active continually. Genes play a crucial role in tissue formation, and the always active proteins prevent regular cell division and growth process.  Mutations that are the leading cause of this syndrome are:

  • Random: Sometimes it develops due to a new mutation in infants who do not have any hereditary predisposition.
  • Inherited: Parent who suffer from Noonan syndrome carries the defective gene (autosomal dominant). Their kids have 50% chances of developing this syndrome.

Noonan Syndrome Symptoms

The signs greatly depend upon the individual, and the characteristics are related to the particular gene enclosing the mutation:

Facial Features

The appearance is one of the key factors to diagnose this disorder. These features are more evident in young children and infants, but vary with increasing age. They become more precise in adulthood and include:

  • Low set ears rotated backward
  • Eyes with droopy lids and down-slanting. The irises are green or pale blue
  • Nose is downcast at the top, with a bulbous tip and broad base
  • Head appears large with a low hairline and prominent forehead on the rear
  • Skin becomes transparent and thin with age
  • Facial features are coarse but become sharper with increasing age, it can become expressionless and droopy
  • The upper lip has a broad peak, and in between the mouth and nose there is a mark or a channel, teeth can be crooked, lower jaw can be small, and the inside mouth roof can be slightly arched.

Heart Diseases

Most patients suffer from inborn heart diseases (congenital heart disease). But some can experience these problems later in life.

  • Hypertrophic Cardiomyopathy (Heart muscle thickening): It can become the reason behind various heart problems.
  • Valve disorders (Pulmonary valve stenosis): It is the pulmonary valve narrowing where the tissue flap disconnects the ventricle (lower right chamber) from the artery which supplies blood to lungs and other parts of the body. This disorder occurs alone or with other heart problems.
  • Irregular Heart Rhythm: Majority of the patients suffer from this problem, it appears with or without the primary heart abnormality.
  • Other defects: It involves other problems like a hole in the heart wall, narrowing (aorta) the primary blood vessel which carries blood to other parts of the body, and narrowing artery that carries oxygen. Image Source:

Slowed Growth

  • Birth weight will be regular as expected, but body growth slows with time
  • Reduced weight and inadequate nutrition due to eating difficulties
  • Hormones essential for growth are insufficient
  • When adults, they might have a short stature
  • Growth seen during teenage is delayed
  • Bone maturity is slow, and sometimes an increase is observed even after teenage

Learning Problems

A wide range of behavioral, mental and emotional issues, which are usually mild
Vision and hearing deficits which complicate learning
An intellectual disability which increases learning disabilities

Musculoskeletal Issues

Broad chest with a recessed sternum (pectus excavatum) or (pectus carinatum) raised sternum
Spine deformities
Short and webbed neck or trapezius (prominent neck muscles)

Eye Conditions

  • Cataracts
  • Brisk eyeball movement (nystagmus)
  • Eye muscle problems like a cross eye (strabismus)
  • Refractive problems like nearsightedness (myopia), farsightedness (hyperopia) or astigmatism

Kidney and Genital Conditions

  • Puberty is retarded in girls and boys both
  • Cryptorchidism or undescended testicles are customary in males
  • Kidney problems are mild and do not occur in every patient, but rarely
  • In females, fertility usually develop, but not in males due to cryptorchidism

Skin Conditions

  • Texture and color of the skin affected
  • Sparse, coarse or curly hair
  • Other skin issues

Lymphatic conditions

The lymphatic system drains out the excess fluid and fights infection. But this disorder can interfere with this system and prevent its normal functioning

  • The problem shows up after birth or originates during teenage or even adulthood
  • Due to improper drainage, the body releases excess fluid (lymphedema) on top of the feet or at the back of the hands

Other Symptoms

  • Nerve issues can lead to hearing problems or structural abnormalities in ear bones
  • Noonan syndrome causes clotting defects where little platelets may result in bruising or excessive bleeding

Noonan Syndrome Complications

  • Bruising & Bleeding: Excessive bleeding is frequent, but it is not usually discovered unless a person has some cuts or wounds or has undergone some surgery or dental work.
  • Cancer Risks: Noonan syndrome affects various parts of the body and also increases risks of specific type of tumors and cancers like leukemia.
  • Slow Development: If the child is negatively affected, he or she might face difficulty with spatial sense. In some cases, developmental challenges are essential to plan the child’s educational and learning needs especially.
  • Urinary Tract Complications: Abnormalities in kidneys increases the risks of UTI and other problems.
  • Lymphatic Complications: Excess fluid gets accumulated in different parts of the body which increases the chance of fluid accumulation in hearts and lungs.

Noonan Syndrome Risk Factors

A person with Noonan syndrome has about 50% chances of passing the gene to his or her baby. But if the baby inherits the defective gene, it might have less or more signs of the disorder than the affected parent.

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Noonan Syndrome Diagnosis

A physician diagnoses this disorder based on the vital signs. Sometimes it is difficult to diagnose due to the preciseness of the features related to the condition. Moreover at times, the disorder is not diagnosed unless the patient has a baby with few or more symptoms of the disease. The syndrome is confirmed after a thorough molecular genetic testing. Early diagnosis can lead to implementing various prevention strategies resulting in a healthy life for patients.

Noonan Syndrome Treatment

Treatment depends upon the particular symptoms and the severity of the signs. Heart and ear problems should be treated in the standard way like for other individuals. Surgery and physical therapy are essential to treat heart problems and learning difficulties.
To prevent disability, early intervention programs are helpful. Bleeding and bruising problems in this syndrome have a variety of causes and require treatment depending upon its cause. Physicians provide blood clotting medicines to prevent excessive bleeding. Lack of growth results in slowed growth and growth hormone treatment is essential.

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