Congenital high airway obstruction sequence (CHAOS): a new case and a review of phenotypic features

Congenital high airway obstruction sequence (CHAOS) has traditionally been defined as airway obstruction with ultrasound evidence of distal airway dilatation, expanded lungs, ascites, and hydrops. It can result from aplasia or intrinsic obstruction to the formation of the upper airway (larynx and trachea) during development. CHAOS is commonly sporadic and there is no known causative gene. In this comprehensive review on CHAOS, we examined 117 reported cases of this sequence and describe a new case. Malformations in addition to high airway obstruction were present in 64/118 (54.2%) of patients. The most frequent anomalies affected the digits and musculoskeletal system, but there was no distinct phenotype or characteristic dysmorphic appearance associated with CHAOS. The ex utero intrapartum therapy (EXIT) procedure has greatly improved survival for these patients and 36/118 (30.5%) were alive at the time of reporting. Only 2 patients out of 12 who underwent laryngotracheoplasty were tracheostomy-free at the time of their reporting. Six out of 13 were able to produce some speech. Our review provides valuable information on associated anomalies and survival in this complex sequence. The phenotypic variability seen in this review of patients makes it likely that the causes of CHAOS are genetically heterogeneous.