Fetal jugular lymph sacs are accumulations of lymphatic fluid in the anterolateral region of the fetal neck. They may be isolated or occur in association with other structural anomalies and in some cases are presenting with an increased nuchal translucency or cystic hygroma. Their significance and the guidelines for the prenatal investigation when identified in the course of routine ultrasonography in pregnancy are still controversial. Our protocol for the investigation of these cases includes microarray analysis and DNA analysis for the Noonan syndrome panel. We report our experience with ten cases of prenatally diagnosed isolated fetal jugular neck cysts identified in the last 5 years (Table 1).

In 10 cases identified by us in the last 5 years, 50% had a pathogenic mutation in a Noonan syndrome Panel, one had trisomy 21 and none had abnormality on microarray analysis (in the case with T21 we stopped the analysis following the QF-PCR results). However, all cases with abnormal results had NT > 3.5 mm or cystic hygroma. This study suggests that the identification of fetal jugular lymph sacs with an increased NT/cystic hygroma is associated with an increased incidence of Noonan syndrome and its related disorders and should instigate mutation analysis of the Noonan syndrome panel.