Jugular lymphatic maldevelopment in Turner syndrome and trisomy 21: different anomalies leading to nuchal edema.

Increased nuchal translucency (NT), morphologically known as nuchal edema, is an ultrasound marker for aneuploidy. Turner syndrome presents with massive NT, called cystic hygroma. Conflicting data exist as to whether cystic hygroma and increased NT are different entities. Both are associated with jugular lymphatic distension. The authors investigated jugular lymphatics of trisomy 21, Turner syndrome, and normal karyotype fetuses. Fetuses were investigated using immunohistochemistry for blood vascular, lymphatic, and smooth muscle cell markers. Trisomy 21 fetuses showed nuchal cavities within the mesenchymal edema negative for endothelial markers. These were extremely large in Turner fetuses, showing similar characteristics. The skin showed numerous dilated lymphatics in the case of trisomy 21 and scanty small lymphatics in Turner fetuses. A jugular lymphatic sac was present in control and trisomy 21 fetuses and was enlarged in trisomy 21 cases. In Turner fetuses, no jugular lymphatic sac was observed. Nuchal edema in trisomy 21 and Turner syndrome appears to be a similar entity caused by different lymphatic abnormalities.