Is Noonan Syndrome Recessive Or Dominant?

Noonan syndrome is an autosomal dominant genetic disorder, in which the growth and development of many body parts are affected due to mutations in one or many genes. Noonan syndrome is a very rare disorder.(1)

Is Noonan Syndrome Recessive Or Dominant?

Noonan syndrome is an autosomal dominant disorder. It means that one set of the altered gene in each cell is enough to cause the disorder. It is a congenital disorder, which means it is evident at birth.(1) This condition may be inherited by a person from his or her parents or may develop as a completely new mutation during the stages of early development.(2)

Noonan syndrome is qualified as a type of RASopathy, which means there is a problem with the cell signaling pathway.(2) Signs and symptoms of Noonan syndrome vary immensely among people. These may range from extremely mild to extremely severe. Also, characteristics or symptoms may be related to the type of gene affected. These signs and symptoms may include.(1)

Abnormal Facial Features- Facial features are one of the most important keys to identify Noonan syndrome. However, these features may be more obvious in infants and young kids and may become subtle as they reach adulthood. These features may include-

  • Wide-set eyes, that are slanting downwards and have droopy eyelids. This may lead to eye problems. Affected irises are green or pale blue in color.
  • Ears look rotated in the backward direction and are low-set
  • The nose looks depressed at the top and has a wide base and a bulging tip
  • Mouth looks like it has a deep groove between the nose and the mouth. Teeth are crooked, the mouth has a highly arched palate with a small lower jaw
  • The face may look expressionless and droopy. Features become sharp with age.
  • The head looks very prominent with a large forehead. It also shows a low back hairline
  • Skin starts to look transparent with age

Heart Conditions:

Children affected with Noonan syndrome are usually born with some form of congenital heart disease. This constitutes some of the important signs and symptoms of Noonan syndrome. Some heart problems manifest themselves later in the life of a child affected by Noonan syndrome. Some common heart problems associated with Noonan syndrome are-

Valve disorders like pulmonary valve stenosis, thickening of the heart muscle or hypertrophic cardiomyopathy, structural defects of heart like a ventricular septal defect or a hole in the heart, pulmonary artery stenosis and coarctation of the aorta. There may also be arrhythmia or irregular heart rhythm, which may or may not be associated with a structural heart defect

Growth Problems:

Noonan syndrome changes the way a child grows. Many kids affected by this condition do not grow at a normal rate. They may face problems like-

  • Poor weight gain and nutrition due to eating difficulties
  • Insufficient levels of growth hormone
  • Growth may continue even into the late teens because this condition delays bone maturity
  • Short stature is more common by adulthood with Noonan syndrome, although some may gain normal height

Musculoskeletal Problems- Some of the most common musculoskeletal problems are abnormally shaped chest, sunken or raised sternum, short neck, webbed neck, spinal deformities, etc.

Learning Disabilities- Most people with Noonan syndrome have unaffected intelligence. However, some may face mild learning and intellectual disabilities

  • Mild emotional, mental and behavioral issues may be seen
  • Learning difficulties may also arise due to hearing and visual difficulties

Bleeding- Excessive bleeding and bruising may be seen due to a low platelet count or clotting defects

Lymphatic Problems- Lymphatic system may be compromised and there may be an excess collection of fluids throughout the body

Genital And Kidney Problems- Genitals and kidney problems may be common, especially in males.(1)

Conclusion

Noonan syndrome is an autosomal dominant disorder. It is an extremely rare disorder and affects the people of all races and sexes equally.

References:

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