Based on the appearance of these two siblings, which pharyngeal arch appears to be most affected?
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.
Pharyngeal arch 1
Pharyngeal arch 2
Pharyngeal arch 3
Pharyngeal arch 4
miscellaneous