Noonan syndrome

Noonan syndrome (NS) is a genetically and phenotypically heterogenous non aneuploidic congenital condition. Affected individuals can bear some clinical features similar to that of Turner syndrome

The estimated incidence is at ~1 in 1000-2500. As individuals have normal number of chromosomes, both males and females can be affected.  

An immense number of clinical features have been described which can be present at varying degrees. These include:

Generalised musculoskeletal
Renal anomalies
  • dilated renal pelves 7,10

The inheritance is autosomal dominant although a significant proportion of cases are sporadic 9. Some cases have a genetic anomaly in chromosome 12q24. 

Antenatal ultrasound

Early 1st trimester ultrasound may show nuchal oedema or a cystic hygroma similar to that of Turner syndrome. With subsequent scanning, some of the above individual clinical features may be present sonographically.

It is named after Jacqueline Noonan, an American (US) paediatric cardiologist  (1921-) 1.

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Article information

rID: 11103
Synonyms or Alternate Spellings:
  • Noonan's syndrome
  • Pseudo-Turner syndrome

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