Persistence of Nuchal Edema and Distended Jugular Lymphatic Sacs in Noonan Syndrome

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Abstract
Noonan syndrome is one of the most common genetic syndromes manifesting at birth. Still, it is diagnosed late, often during infancy. Diagnosis is difficult because prenatal ultrasound findings are unspecific and the dysmorphias after birth can be subtle. Two women were referred to our university hospital because of an increased nuchal translucency in the first trimester of pregnancy. Further ultrasound examination showed the bilateral presence of distended jugular lymph sacs. Karyotyping revealed euploidy in both fetuses. The second trimester ultrasound scan showed a persistence of the jugular lymph sacs together with a nuchal fold, indicating a disturbed lymphatic development. There were no other anomalies. In 1 case the jugular lymph sacs containing newly formed lymph node tissue remained visible until 35 weeks' gestation. Both newborns were diagnosed with Noonan syndrome after birth. Postnatal echocardiography revealed a mild pulmonary stenosis. Distension of the jugular lymph sacs is known to cause nuchal edema and normally resolves after the first trimester. In case of persistence of the jugular lymphatic sacs beyond the second trimester of pregnancy, the diagnosis of Noonan syndrome and subsequent DNA testing should be considered.