Auriculocondylar syndrome

Auriculocondylar syndrome (ACS) is a rare craniofacial malformation syndrome characterized by mandibular hypoplasia and question-mark ears (QME). QMEs, consisting of a specific defect at the lobe-helix junction, can also occur as an isolated anomaly. Studies have indicated the essential role of endothelin 1 (EDN1) signaling through the endothelin receptor type A (EDNRA) in patterning the mandibular portion of the first pharyngeal arch. Mutations in the PLCB4 and GNAI3, predicted to function as signal transducers downstream of EDNRA, have recently been reported in ACS.