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Is Noonan Syndrome Life-Threatening?

Reviewed on 6/19/2020

What Is Noonan Syndrome?

Noonan syndrome is a genetic disorder.
Noonan syndrome is a genetic disorder.

Noonan syndrome is a genetic condition in which patients have short stature, unusual facial features, chest deformity, and congenital heart disease.

What Are Symptoms and Signs of Noonan Syndrome?

Symptoms and signs of Noonan syndrome range from mild to severe and may include the following:

  • Distinctive facial features
    • Wide-spaced eyes that slant downward
    • Droopy eyelids
    • Light-colored eyes (pale blue or green)
    • Low-set ears that are turned backwards
    • Short neck
    • Excess skin and low hairline in the back (adults)
    • Nose is depressed at the top, with a broad base and bulbous tip
    • Deep groove in the area between the nose and mouth
    • Crooked teeth
    • Highly arched palate in the mouth
    • Small lower jaw
    • Prominent forehead
    • Thin, transparent skin with age
  • Congenital heart defects
  • Growth insufficiencies, short stature in adulthood
  • Scoliosis
  • Musculoskeletal issues
  • Learning disabilities
  • Vision or hearing problems
  • Bleeding disorders
    • Bruising
    • Nosebleeds
    • Prolonged bleeding following injury or surgery
    • Excessive bleeding during menstruation (menorrhagia) or childbirth (rare)
  • Lymphatic issues/lymphedema
    • Fluid buildup under the skin (edema)
  • Delayed puberty
  • Genital problems
    • Undescended testes (cryptorchidism), which may contribute to infertility
  • Kidney (renal) issues
  • Skin issues

What Causes Noonan Syndrome?

Noonan syndrome is a genetic disorder caused by a genetic mutation. Mutations may be inherited, that is, passed along from one or both parents, or random, where it develops from a new mutation in the child.

A parent with Noonan syndrome has a 50% chance of passing on the genetic mutation to their child.

How Do Doctors Diagnose Noonan Syndrome?

Noonan syndrome is often diagnosed based on the characteristic signs, along with a complete physical and neurologic exam. Genetic testing can help confirm the diagnosis.

Medical professionals will test patients with Noonan syndrome to determine which symptoms they have. Tests may include the following:

  • Heart evaluation: including echocardiogram (echo) and electrocardiogram (ECG/EKG)
  • Vision and hearing evaluation
  • Coagulation (blood clotting) screen
  • Kidney ultrasound examination
  • Developmental assessment
  • Full blood workup
  • Imaging studies
    • Brain and cervical spine magnetic resonance imaging (MRI) for neurologic symptoms
    • X-rays for chest and back abnormalities and to evaluate the patient for Noonan-like/multiple giant cell lesion syndrome (NS/MGCLS)

What Is the Treatment for Noonan Syndrome?

Treatment of Noonan syndrome aims to relieve symptoms and may include cardiac therapy, growth hormone therapy, physical and speech therapy, eye treatment, bleeding disorder management, treatment of lymphatic problems, and urologic therapy (in males).

  • Low growth rate may be treated with growth hormone such as somatropin (Norditropin).
  • Heart problems may be treated with medications or surgery.
  • Vision problems may be corrected with eyeglasses, and cataracts may require surgery.
  • Hearing problems may warrant cochlear implants.
  • Bleeding problems may be treated with anticoagulants.
  • Learning disabilities and developmental delays may be treated with special education, physical therapy, and speech therapy.
  • If one or both testicles remain undescended, surgery may be recommended.

What Are Complications of Noonan Syndrome?

The following are complications of Noonan syndrome:

  • Excessive bleeding and bruising
  • Developmental delays and learning disabilities
  • Lymphatic complications such as fluid buildup under the skin (edema), or fluid around the heart or lungs
  • Increased risk of urinary tract infections (UTI)
  • Increased risk of certain types of cancer
    • Leukemia
    • Neuroblastoma
    • Embryonal rhabdomyosarcoma
  • Fertility problems in males

What Is the Life Expectancy for Noonan Syndrome?

Symptoms and signs of Noonan syndrome range from mild to severe. Some patients with mild symptoms and signs will have a normal life expectancy, while others with severe symptoms and signs may have a shortened lifespan.

The highest risk of death is in young adults who have hypertrophic cardiomyopathy that was diagnosed when they were under 2 years old.

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Reviewed on 6/19/2020
References
McGovern, Margaret M. "Noonan Syndrome." May 18, 2020. Medscape.com. <http://emedicine.medscape.com/article/947504-overview>.
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