Frequency of Aortic Dilation in Noonan Syndrome

Abstract

Noonan syndrome (NS) is a genetic disorder caused by mutations altering proteins relevant to RAS/mitogen-activated protein kinase signal transduction. Cardiac involvement is common, most prevalently pulmonary valve stenosis and hypertrophic cardiomyopathy. Because abnormal mitogen-activated protein kinase signaling contributes to the aortopathy in Marfan syndrome and with rare reports of aortic aneurysm in NS, we undertook a retrospective study of ascending aortic anatomy in 37 patients with NS and without confounding medical conditions. Age ranged from 0.6 to 32 years. Based on the most recent echocardiogram, the aortic annulus and root were dilated in the cohort (mean z scores of 1.14 and 0.98, respectively, p <0.005) but the sinotubular junction and ascending aorta were not (mean z scores of 0.05 and 0.19, respectively). The aortic root was aneurysmal (>2 z scores) in 8 subjects (21.6%). PTPN11 mutations were present in 14 subjects, whose aortic status was similar to the cohort overall. Comparison of age and z scores revealed a modest tendency for the aortic annulus and root to dilate over time. Among 13 subjects with multiple imaging studies over an average of 6.8 years, the average z score increased to 0.78 and 0.39 for the aortic annulus and root, respectively. Multivariate analysis revealed that age accounted for 7.0% and 11.0% of the variance in the aortic annular and root diameters, respectively. In conclusion, we found that aortic annular dilation and aortic root aneurysm are prevalent in NS, often presenting during childhood and progressing over time. Further study is needed to identify potential risks associated with these abnormalities.