Noonan syndrome
| Noonan syndrome | |
|---|---|
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| A 12-year-old girl with Noonan syndrome. Typical webbed neck. Double structural curve with rib deformity. | |
| Classification and external resources | |
| Specialty | Medical genetics, pediatrics |
| ICD-10 | Q87.1 |
| ICD-9-CM | 759.89 |
| OMIM | 163950 605275 609942 610733 611553 |
| DiseasesDB | 29094 |
| MedlinePlus | 001656 |
| eMedicine | article/947504 |
| Patient UK | Noonan syndrome |
| MeSH | D009634 |
| GeneReviews | |
Noonan syndrome (NS) is a relatively common autosomal dominant congenital disorder and is named after Jacqueline Noonan, a pediatric cardiologist. It is referred to as the male version of Turner's syndrome; however, the genetic causes of Noonan syndrome and Turner syndrome are distinct. The principal features include congenital heart defect (typically pulmonary valve stenosis; also atrial septal defect and hypertrophic cardiomyopathy), short stature, learning problems, pectus excavatum, impaired blood clotting, and a characteristic configuration of facial features including a webbed neck and a flat nose bridge. NS is a RASopathy, and is one of several disorders that are caused by a disruption of RAS-MAPK signaling pathway.
It is believed that between approximately 1 in 1,000 and 1 in 2,500 children worldwide are born with NS. It is one of the most common genetic syndromes associated with congenital heart disease, similar in frequency to Down syndrome. However, the range and severity of features can vary greatly in patients with NS. Therefore, the syndrome is not always identified at an early age.
Up to ~85% of people with NS have one of the following heart defects:
Recurrence in siblings and apparent transmission from parent to child has long suggested a genetic defect with autosomal dominant inheritance and variable expression. Mutations in the Ras/mitogen activated protein kinase signaling pathways are known to be responsible for ~70% of NS cases.
A person with NS has up to a 50% chance of transmitting it to their offspring. The fact that an affected parent is not always identified for children with NS suggests several possibilities:
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