Based on the appearance of these two siblings, which pharyngeal arch appears to be most affected?: (A) Pharyngeal arch 1, (B) Pharyngeal arch 2, (C) Pharyngeal arch 3, (D) Pharyngeal arch 4
Answer is A. Here both siblings show mandibular hypoplasia. Mandible develops from 1st pharyngeal arch Pierre Robin sequence and Treacher Collins syndrome are both associated with mandibular hypoplasia.