NOONAN SYNDROME AND TURNER SYNDROME: OVERLAP OF CARDIAC PHENOTYPES.

Background Turner syndrome (TS) and Noonan syndrome (NS) share some phenotypical similarities: short stature, pterigium colli, cubitus valgus and congenital lymphedema. Nevertheless, patients (pts) with NS present anatomic types of congenital heart disease (CHD) different from those of pts with TS: pulmonary stenosis and hypertrophic cardiomyopathy (HCM) are common in NS while bicuspid aortic valve and aortic coarctation (AC) are the most common in TS. Among the series of pts with NS and TS we selected the cases with overlap of cardiac phenotypes. Methods Seventy pts with karyotype-proven TS and 136 pts with clinical diagnosis of NS received a complete cardiac evaluation, including chest radiography, cardiac examination, ECG and transthoracic echocardiography. Among the 136 propositi with NS, AC was diagnosed in 12 pts (8.8%) and 1 pt (1.4%) with TS mosaicism was affected by severe concentric HCM. Discussion Although the spectrum of CHD are different, some overlap of cardiac phenotypes are evident between these two syndromes. For children with NS and AC one explanation can be the presence of another genetic locus for NS different from PTPN11 (recently mapping to 12q24.1) and located at or near the critical region for TS (Xp). The HCM in the subject with TS can be due to addition point mutation of PTPN11. Other explanations including the random association can not be ruled out.