All faces are inherently asymmetric but severe asymmetry may be the result of hemifacial microsomia (HFM).
Sometimes called Parry-Romberg disease, involves an autoimmune response where the subcutaneous fat of the face wastes away leaving significant contour defects.
Bell’s palsy is form of facial paralysis related to dysfunction of the facial nerve.
A small lower jaw (mandible) can lead to abnormal tongue positioning causing a cleft palate which may obstruct the airway in some newborns.
Treacher collins syndrome can be genetically inherited or occur as new mutations and cause a pattern of facial clefting as well as a small lower jaw.