The jaw can be missing, deformed, or incompletely developed at birth.
Jaw defects include
Micrognathia is a small lower jaw (mandible). Pierre Robin sequence and Treacher Collins syndrome, which are disorders characterized by several defects in the head and face, are associated with a small lower jaw. If the lower jaw is too small, the infant may have difficulty eating or breathing. Surgery may correct or diminish the problem.
Agnathia, a condition in which a part of or the entire lower jaw is missing, is a severe malformation. Often the infant also has abnormalities of the ears, temporal bone, saliva glands, the muscles used in chewing, and facial nerve. Doctors assess the degree of jaw underdevelopment with x-rays and computed tomography (CT) of the face. Treatment of agnathia consists of reconstructive surgery with bone grafts and other tissue grafts to improve the appearance and function of the jaw.
Maxillary hypoplasia is underdevelopment of the upper jaw (maxilla). It causes a flat mid-face, which makes the lower jaw appear to stick out.