This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Surgery
Which one of the following is the primary defect in pierre Robin syndrome? 
Select and explain. 
A. Micrognathia, B. Glossoptosis, C. High arched palate, D. Cleft palate
A: Micrognathia
Answer: A: Micrognathia 
Explanation: 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