Both affected males and females have apparently normal chromosome complements and normal gonadal function. The phenotypic appearance of the female is that of a patient with Turner syndrome: short stature, webbed neck, shield chest, and cardiac malformations. The cardiac lesions, however, are different. Pulmonic stenosis is most frequent in Noonan syndrome as opposed to aortic coarctation in Turner syndrome. Apparently this syndrome results from a second mutant gene or genes. In the past these patients have been referred to as male Turner's or Turner's with normal chromosomes. Noonan's are fertile and transmit the trait as an autosomal dominant with variable expression.