CHAOS, or Congenital High Airway Obstruction Syndrome.
DISCUSSION
Prevalence: 1 in 50,000 births..
Pathology: Agenesis or stenosis of a segment of the upper airways at the level of the trachea or larynx. In a few cases the condition results from the presence of laryngeal cysts or laryngeal web.
Ultrasound features become evident ≥16 weeks’ gestation. The lungs are massively enlarged and hyperechogenic resulting in compression of the heart and development of ascites. The bronchial tree is dilated and the diaphragm inverted.
Associated abnormalities: The incidence of chromosomal abnormalities is not increased. Genetic syndromes are found in >50% of cases. The most common is Fraser syndrome (autosomal recessive; microphthalmia, facial cleft, tracheal atresia, bilateral renal agenesis, heart defects, syndactyly or polydactyly).
Fetal MRI could help identify the location and type of obstruction.
Delivery at hospital with neonatal intensive care and pediatric surgery.
Method: cesarean section with EXIT procedure and tracheostomy.
Prognosis: Highly lethal condition with almost all cases dying in the neonatal period.
There are a few case reports of spontaneous resolution in utero, either because of dilatation of a stenotic segment between the larynx and the trachea or even development of a tracheoesophageal fistula with drainage of the bronchial fluid into the esophagus.
Recurrence:
Isolated: no increased risk.
Fraser syndrome: 25%.