Abnormal facial shape Flat face 2013-10-13T01:49:13Z UMLS:C1853241 Flat facies HP:0012368 Flat facial shape Flat facial profile A useful guide is to imagine that a line connecting the glabella to the anterior most part of the mandible touches the top of the philtrum where it meets the base of the columella. The glabella is the most prominent point on the frontal bone above the root of the nose. If the superior philtrum is anterior to this line the face is convex, if the superior philtrum is posterior to this line the face is concave. Flat face Absence of concavity or convexity of the face when viewed in profile.