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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