Noonan syndrome

Also known as: familial Turner syndrome, female pseudo-Turner syndrome, male Turner syndrome, Noonan-Ehmke syndrome, Noonan's syndrome, NS, pseudo-Ullrich-Turner syndrome, Turner-like syndrome, Turner phenotype with normal karyotype, Turner syndrome in female with X chromosome, Ullrich-Noonan syndrome

Definition

Genetics Home Reference

Noonan syndrome is a condition that affects many areas of the body. It is characterized by mildly unusual facial features, short stature, heart defects, bleeding problems, skeletal malformations, and many other signs and symptoms.

People with Noonan syndrome have distinctive facial features such as a deep groove in the area between the nose and mouth (philtrum), widely spaced eyes that are usually pale blue or blue-green in color, and low-set ears that are rotated backward. Affected individuals may have a high arch in the roof of the mouth (high-arched palate), poor teeth alignment, and a small lower jaw (micrognathia). Many children with Noonan syndrome have a short neck, and both children and adults may have excess neck skin (also called webbing) and a low hairline at the back of the neck.

Between 50 and 70 percent of individuals with Noonan syndrome have short stature. At birth, they are usually a normal length and weight, but growth slows over time. Abnormal levels of growth hormone, a protein that is necessary for the normal growth of the body's bones and tissues, may contribute to the slow growth.

Individuals with Noonan syndrome often have either a sunken chest (pectus excavatum) or a protruding chest (pectus carinatum). Some affected people may also have an abnormal side-to-side curvature of the spine (scoliosis).

Most people with Noonan syndrome have some form of critical congenital heart disease. The most common heart defect in these individuals is a narrowing of the valve that controls blood flow from the heart to the lungs (pulmonary valve stenosis). Some have hypertrophic cardiomyopathy, which enlarges and weakens the heart muscle.

A variety of bleeding disorders have been associated with Noonan syndrome. Some affected individuals have excessive bruising, nosebleeds, or prolonged bleeding following injury or surgery. Rarely, women with Noonan syndrome who have a bleeding disorder have excessive bleeding during menstruation (menorrhagia) or childbirth.

Adolescent males with Noonan syndrome typically experience delayed puberty. They go through puberty starting at age 13 or 14 and have a reduced pubertal growth spurt that results in shortened stature. Most males with Noonan syndrome have undescended testes (cryptorchidism), which may contribute to infertility (inability to father a child) later in life. Females with Noonan syndrome can experience delayed puberty but most have normal puberty and fertility.

Noonan syndrome can cause a variety of other signs and symptoms. Most children diagnosed with Noonan syndrome have normal intelligence, but a few have special educational needs, and some have intellectual disability. Some affected individuals have vision or hearing problems. Affected infants may have feeding problems, which typically get better by age 1 or 2 years. Infants with Noonan syndrome may be born with puffy hands and feet caused by a buildup of fluid (lymphedema), which can go away on its own. Older individuals can also develop lymphedema, usually in the ankles and lower legs.

Some people with Noonan syndrome develop cancer, particularly those involving the blood-forming cells (leukemia). It has been estimated that children with Noonan syndrome have an eightfold increased risk of developing leukemia or other cancers over age-matched peers.

Noonan syndrome is one of a group of related conditions, collectively known as RASopathies. These conditions all have similar signs and symptoms and are caused by changes in the same cell signaling pathway. In addition to Noonan syndrome, the RASopathies include cardiofaciocutaneous syndrome, Costello syndrome, neurofibromatosis type 1, Legius syndrome, and Noonan syndrome with multiple lentigines.

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Orphanet

Noonan Syndrome (NS) is characterised by short stature, typical facial dysmorphism and congenital heart defects.

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Symptoms

Medical Term Other Names Description
Micrognathia Lower jaw hypoplasia, Mandibular deficiency, Retrusion of lower jaw, Hypoplastic mandible condyle, Small mandible, Decreased projection of lower jaw, Micrognathia of lower jaw, Mandibular retrognathia, Mandibular retrusion, Decreased size of lower jaw, Micromandible, Underdevelopment of lower jaw, Hypotrophic mandible, Hypotrophic lower jaw, Robin mandible, Little mandible, Underdevelopment of mandible, Small jaw, Decreased size of mandible, Hypoplastic mandible, Little lower jaw, Decreased projection of mandible, Mandibular micrognathia, Lower jaw retrognathia [more] Developmental hypoplasia of the mandible.
Pallor Paleness Abnormally pale skin.
Pectus carinatum Pigeon chest A deformity of the chest caused by overgrowth of the ribs and characterized by protrusion of the sternum.
Infertility
Abnormal facial shape Dysmorphic facial features, Facial Dysmorphism, Deformity of face, Distortion of face, Unusual facial appearance, Funny looking face, Dysmorphic facies, Unusual facies, Malformation of face, Abnormal morphology of the face, Distinctive facies [more] An abnormal morphology (form) of the face or its components.
Redundant neck skin Redundant skin folds of neck, Redundant skin over the neck, Redundant nuchal skin, Excess neck skin, Excess skin over the neck [more] Excess skin around the neck, often lying in horizontal folds.
Hypertelorism Increased distance between eye sockets, Increased distance between eyes, Increased interpupillary distance, Widely spaced eyes, Excessive orbital separation, Widened interpupillary distance, Ocular hypertelorism, Wide-set eyes [more] Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes).
Low-set ears Melotia, Lowset ears Upper insertion of the ear to the scalp below an imaginary horizontal line drawn between the inner canthi of the eye and extending posteriorly to the ear.
Short neck Decreased cervical height, Cervical shortening, Decreased cervical length, Decreased length of neck [more] Diminished length of the neck.
Abnormal heart morphology Congenital heart defects, Abnormally shaped heart, Cardiac anomalies, Abnormality of cardiac morphology, Abnormality of the heart [more] Any structural anomaly of the heart.
Pectus excavatum Funnel chest A defect of the chest wall characterized by a depression of the sternum, giving the chest ("pectus") a caved-in ("excavatum") appearance.
Cardiomyopathy A myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality.
Menorrhagia Hypermenorrhea, Abnormally heavy bleeding during menstruation Prolonged and excessive menses at regular intervals in excess of 80 mL or lasting longer than 7 days.
Short stature Decreased body height, Height less than 3rd percentile, Small stature, Stature below 3rd percentile [more] A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).
Cryptorchidism Undescended testes, Undescended testis, Cryptorchism [more] Testis in inguinal canal. That is, absence of one or both testes from the scrotum owing to failure of the testis or testes to descend through the inguinal canal to the testis.
Intellectual disability Nonprogressive intellectual disability, Poor school performance, Mental-retardation, Dull intelligence, Nonprogressive mental retardation, Mental deficiency, Mental retardation, nonspecific, Low intelligence [more] Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.
Lymphedema Lymphoedema, Onset of lymphedema around puberty, Lymphatic obstruction [more] Localized fluid retention and tissue swelling caused by a compromised lymphatic system.
Feeding difficulties Feeding problems, Poor feeding Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Delayed puberty Delayed pubertal development, Pubertal delay, Delayed pubertal growth [more] Passing the age when puberty normally occurs with no physical or hormonal signs of the onset of puberty.
Pulmonic stenosis Narrowing of pulmonic valve, Pulmonic valve stenosis, Pulmonary stenosis, Pulmonary valve stenosis [more] A narrowing of the right ventricular outflow tract that can occur at the pulmonary valve (valvular stenosis) or just below the pulmonary valve (infundibular stenosis).
Abnormality of cardiovascular system morphology Cardiovascular malformations, Heart defect Any structural anomaly of the heart and great vessels.
Leukemia Blood cancer A cancer of the blood and bone marrow characterized by an abnormal proliferation of leukocytes.
Neurofibromas multiple neurofibromas, Neurofibromatosis, Neurofibromata [more] The presence of multiple cutaneous neurofibromas.
High, narrow palate Narrow and high arched palate, High arched palate, Narrow, high-arched roof of mouth, Narrow, highly arched palate, Gothic palate, High vaulted palate, Narrow, highly arched roof of mouth [more] The presence of a high and narrow palate.
Hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality.
Epistaxis Frequent nosebleeds, Nose bleeding, Nosebleed, Bloody nose [more] Epistaxis, or nosebleed, refers to a hemorrhage localized in the nose.

Other Classifiers and IDs

  • OrphaNet: ORPHA:648
  • MedDRA: 10029748
  • MeSH: D009634
  • UMLS: C0028326
  • OMIM: 163950