Long face syndrome, also referred to as skeletal open bite is a condition generally caused by childhood mouth breathing. However, a decreased airway size due to edema, an obstruction or genetics are other contributing factors. If the cause is mouth breathing, it generally occurs when children are unable to breathe through their noses, which changes the child's bite while they are still growing.
The condition's most striking symptom is an excessively long lower face height.
Treatment for the cosmetic effects of long face syndrome after childhood where little potential for growth is possible is surgical. The surgery performed is normally a dentofacial osteotomy.
References
Long face syndrome Wikipedia(Text) CC BY-SA