Which one of the following is the primary defect in Pierre Robbin syndrome?

This syndrome described by Pierre Robbin includes retrognathia or micrognathia (retrognathia means abnormal posterior positioning of one or both jaws, paicularly the mandible relative to the facial skeleton) glossoptosis (posteriorly displaced tongue) airway obstruction An incomplete cleft palate is associated in approx. 50% of these patients. In these pts. the micrognathia (small jaw) or retrognathia causes the tongue to fall back towards the post. pharyngeal wall. This results in obstruction of the airway on inspiration.