Why it's not the other choices:
Cystic hygroma: if you see this, associate it with Turners.
Thyroglossal duct cyst: moves up and down with swallowing and doesnt cause the sx presented in this stem.
Tracheomalacia: In tracheomalacia, the cartilage of the windpipe does not develop properly in utero, leaving them weak and flaccid. The weakened walls are likely to collapse and cause an obstruction of the airway. Yes it can cause stridor but has no relation or association with maternal Graves as the cause and also doesnt present as a neck mass.
Vascular ring: occurs when the aorta or its branches form a complete ring around the trachea and the esophagus. This happens when certain parts of the aorta that normally disappear during fetal development persist abnormally. Sx are dysphagia and cough. Most sx are so mild that children who have it often go years without diagnosis. Also doesnt present as a neck mass.
Hyperthyroidism in the newborn
submitted by โbingcentipede(356)
IgG antibodies can cross the placenta, leading to thyroid enlargement. This can also explain the stridor and issues with respiration in the newborn. Essentially, this is causing neonatal Graves disease.
From UpToDate: "Neonatal Graves disease refers to the hyperthyroidism that is seen in a small percentage of infants born to mothers with Graves disease. Although neonatal Graves disease is usually self-limited, it can be severe, even life-threatening, and have deleterious effects on neural development"