<prompt> Pierre Robin sequence is caused by defect in development of which pharyngeal arch?IIIIVNone of the above  <response>: Robin sequence may occur independently or in association with other syndromes and malformations. Like Treacher Collins syndrome, Robin sequence alters first-arch structures, with development of the mandible most severely affected. Infants usually have a triad of micrognathia, cleft palate, and glossoptosis posteriorly placed tongue Ref: Langmans embryology 11th edition Chapter 16. 