Prenatal diagnosis of Noonan syndrome in fetuses with increased nuchal translucency and a normal karyotype.

Objective: Noonan syndrome (NS), one of the most common RASopathies, has an estimated incidence of 1 in 1,000-2,500 live births. In the prenatal period increased nuchal translucency, hygroma colli, hydrops fetus, congenital heart disease, kidney defects, larger amount of amniotic fluid can be observed in affected fetuses with this syndrome. In the fetuses with normal karyotype and no microdeletion/microduplication syndromes the examination of selected genes for RASopathies was added.

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.