Criteria

Noonan syndrome diagnostic criteria[1][42]

Several scoring systems have been devised to help the diagnostic process.[42][51] The most recent scoring system was developed in 1994.[42] In this system, NS is defined as typical facial features plus 1 major or 2 minor clinical characteristics, or suggestive facial features plus 2 major or 3 minor clinical characteristics. However, the typical facial features can be subtle and often require evaluation from an experienced dysmorphologist. Molecular testing for mutations in the genes known to cause NS may be required if the diagnosis is in question.

Major characteristics

  • Cardiac: pulmonary valve stenosis and/or typical ECG

  • Height: <third centile

  • Chest wall: pectus carinatum/excavatum

  • Family history: first-degree relative with definite diagnosis

  • Cognitive impairment, cryptorchidism, lymphatic dysplasia: all 3 present.

Minor characteristics

  • Cardiac: other defects than those described as major characteristics

  • Height: <tenth centile; short stature may be present at birth or postnatal in origin

  • Chest: broad thorax

  • Family: first-degree relative with suggestive diagnosis

  • Cognitive impairment, cryptorchidism, lymphatic dysplasia: any of the 3 present.

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