Treacher Collins syndrome (TCS) is a rare genetic disorder that tends to involve underdevelopment of the facial skeleton, cheekbones, jaws, palate and mouth which can lead to breathing and eating difficulties. In addition, affected individuals may also have a downward slant of the opening between the upper and lower eyelids (palpebral fissures) and anomalies of external and middle ear structures, which may result in hearing loss. The specific symptoms and physical characteristics associated with TCS can vary greatly from one individual to another.