The maxilla often is associated with a thin zygomatic arch and small or absent maxillary sinuses.
Although young patients typically exhibit a relatively normal jaw relationship, as the individuals age, a short lower face height, acute gonial angle, anterior inclination of the mandible, and mandibular prognathism develop. Clinicians believe that these changes may be from inadequate vertical growth of the maxilla and hypoplastic alveolar ridge development caused by delay or lack of eruption of the permanent teeth.
Computed tomography (CT) studies have demonstrated a decreased thickness of the masseter muscle in some patients. This finding may be related to hypoplasia of the zygomatic arch resulting in hypofunction of the attached masseter muscle.