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In midfacial hypoplasia, the center of the face develops more slowly than the eyes, forehead, and lower jaw. When mild, this is generally considered to be a normal, harmless genetic variation. In more severe cases, however, the condition is so pronounced that both appearance and health may be affected. In these instances, the hypoplasia is often a symptom of other health issues or genetic disorders.
Human genetics allow for infinite variations in facial construction. In individuals with mild benign midfacial hypoplasia, normal differences in appearance result in the features in the middle of the face being smaller, in comparison, than the features at the top and the bottom of the face. The effect is a forehead, lower jaw, and eyes that appear unusually large. In more pronounced instances, the jaw may jut noticeably forward, and the eyes may appear to bulge.
When midfacial hypoplasia is marked or easily identifiable at birth, it usually indicates a medical problem affecting the underlying structures of the face. In Crouzon Syndrome, for example, the condition results when the plates of the skull fuse together before full growth of the skull is completed. Treatment of this genetic condition usually involves removal or fracture of the bones of the skull.
Midfacial hypoplasia has also been associated with achondroplasia, the most common type of dwarfism. This disorder primarily affects the long bones of the legs and arms but can also lead to abnormal craniofacial development. In dwarfism, the extent of the hypoplasia is generally mild and requires intervention only when severe enough to cause complications.
Regardless of its cause, severe midfacial hypoplasia can often result in obstructive sleep apnea (OSA). Patients with OSA experience intermittent cessations of breathing while sleeping and often suffer symptoms such as severe headache, insomnia, and high blood pressure as a result. Obstructive sleep apnea is most commonly treated by applying enough air pressure to keep the airways open via a continuous positive airway pressure (CPAP) machine that is worn by the patient while sleeping. For those patients who have dangerously prolonged periods of not breathing, most other options are surgical. In jaw surgery, excess tissue in the airway is removed or a breathing tube is inserted directly into the throat.
Pronounced midfacial hypoplasia can also result in misalignment of the jaws and eyelids. In the former, the upper and lower jaws do not meet, resulting in difficulties with chewing and speech. In the later, the eyelids are unable to close completely, and persistent dry eyes and vision problems are common. Both conditions require plastic surgery to correct completely.