More or less CHAOS: Case report and literature review suggesting the existence of a distinct subtype of congenital high airway obstruction syndrome

Congenital obstruction of the upper airway (CHAOS) is a rare, usually lethal abnormality. A literature review of 36 prenatally diagnosed cases of CHAOS and the analysis of our own case suggest the existence of a distinct subtype of CHAOS, raising important implications for diagnosis and management. Serial fetal ultrasound examinations at 17-23 weeks' gestation showed hyperechoic and enlarged lungs, mediastinal shift, flattened diaphragm, polyhydramnios and apparently fluid-filled esophagus, findings interpreted as bilateral cystic adenomatoid malformation Type III. Ultrasound findings normalized around 32 weeks. The diagnosis of CHAOS was made after birth at term by direct laryngoscopy prompted by ventilatory difficulties and failed attempts at intubation. A pinhole opening posterior to the cricoid cartilage allowed the passage of an endotracheal tube. Based on observations in our case and those of five similar cases in the literature, we describe for the first time a subtype of CHAOS that is characterized by minor pharyngotracheal or laryngotracheal communications and associated with a less severe natural history and even resolution of ultrasound findings. In spite of this, a high index of awareness should be maintained because resolution of ultrasound findings does not necessarily indicate resolution of underlying pathology.