Which one of the following is the primary defect in pierre Robin syndrome?

Pierre Robin Sequence Pierre Robin sequence remains the most common syndrome in clefts of the lip and palate Pierre Robin sequence is characterized by three pathognomic findings Microretrognatia ( Primary Defect) Glossoptosis Respiratory distress Pierre Robin sequence may or may not be associated with a palate cleft Micrognathia prevents the natural caudal migration of the tongue resulting in the deformity Functional consequences include intermittent respiratory obstruction and obstructive sleep apnoea that may affect feeding growth, and safety of the airway Posteriorly displaced tongue (glossoptosis), which is associated with early respiratory and feeding difficulties. Treatment : Beverly--Douglas procedure (Tongue is fixed anteriorly) Ref: schwaz's principle of surgery 10th edition Pgno : 1848