Noonan syndrome from a fetopathologist perspective.

We present our experience with four cases of fetal autopsies with abnormal prenatal ultrasound findings and suspicion of Noonan syndrome. These were fetuses from the 17th to the 24th age of gestation (GA). In all cases, prenatal ultrasound examination recorded increased nuchal translucency (NT) and presence of lymphatic neck sacs. Some fetuses showed signs of fetal hydrops and polyhydramnion was found. Similar signs and congenital developmental defects were confirmed in the autopsy examination. These were primarily signs of developing fetal hydrops with increased nuchal edema, in some cases up to the character of cystic hygroma, pleural and abdominal effusions, congenital heart and kidney defects, skeletal defects and facial dysmorphism. A karyotype was examined in all cases without chromosome aneuploidy. The diagnosis of NS was confimed by subsequent genetic analysis of causal gene mutations (mainly PTPN11, KRAS, RAF 1,). Our cases demonstrate a wide range of signs of prenatal presentation of this syndrome. Because of wide differential diagnosis, summarizing prenatal ultrasound findings, autopsy examination and molecular genetic testing is essential.