Table II.

Diagnostic criteria for Noonan syndrome

Feature	A = Major	B = Minor
Facial	Typical facial dysmorphology (also change with age)	Suggestive facial dysmorphology
Cardiac	Pulmonary valve stenosis, HOCM and/or ECG Typical of Noonan syndrome	Other defect
Height	< P3*	< P10*
Chest wall	Pectus carinatum/excavatum	Broad thorax
Family history	First-degree relative with definite Noonan syndrome	First-degree relative with suggestive Noonan syndrome
Other features	Mental retardation, cryptorchidism, and lymphatic vessel dysplasia	One of mental retardation, cryptorchidism, or lymphatic vessel dysplasia

HOCM – hypertrophic obstructive cardiomyopathy;

^*P3 and P10 refer to percentile lines for height according to age, with the normal range of variation defined as P3-P97 inclusive: definitive Noonan syndrome: 1 “A” plus one other major sign or two minor signs; 1 “B” plus two major signs or three minor signs. Adapted with permission from van der Burgt I, Berends E, Lommen E, van Beersum S, Hamel B, Mari-man E. Clinical and molecular studies in a large Dutch family with Noonan syndrome. Am J Med Genet 1994; 53: 187-91.