Mandibular facial osteogenesis imperfecta is a group of syndromes characterized clinically by low zygomatic bone, auricular deformity and underdevelopment of the lower award due to abnormal development of the first and second gill arches during the embryonic period resulting in their evolved structures, especially the mandible and zygomatic bone. [Alias] Multiple facial anomalies syndrome; first gill arch syndrome; mandibular facial osteogenesis imperfecta syndrome; Treacher
Collins syndrome; Franceschetti-Zwahlen-Klein syndrome. [Etiology] Autosomal dominant. [Pathogenesis] At 6-8 weeks of embryonic life, the neural crest cells of the facial and auditory primordia (the predecessors of the mesoderm and ectoderm of the first and second gill arches) are impaired in development, resulting in a decrease in the mesenchyme that will evolve into musculoskeletal structures in the first and second gill arches, eventually affecting 9 the development of the zygomatic bone, zygomatic arch, maxilla, mandible, external ear, and middle ear. [Clinical manifestations] with highly characteristic facial features. Facial deformities: The zygomatic bones are small and low, and the zygomatic arches are absent or vestigial, thus forming obvious depressions at the outer edge of the orbits and the roots of the zygomatic arches, and the degree of left and right involvement may be different and the facial shape is asymmetrical. Ophthalmoplegia: Due to the underdevelopment of the zygomatic bones supporting the outer and lower orbital margins, the lid fissure tilts outward and downward, and there is often a small defect in the outer third of the lower eyelid, where the eyelid is slightly ectropioned. Otologic deformities: auricular deformities, such as aural atresia or downward misalignment, atresia of the external auditory canal, malformation or absence of the auditory tuberosity are also common, and aural atresia or gill fistula can be seen on the line from the ear screen to the corner of the mouth. Malformations of the oral and maxillary system: rounded mandibular angle, short or absent mandibular ascending branch, receding chin, cleft palate or incomplete palatopharyngeal closure are also common, and cleft mouth is often large and misaligned. Nasal deformity: the nasal bridge is elevated so that the frontal angle of the nose disappears, and there may be nasal cartilage hypoplasia, posterior nostril atresia and other deformities. [Diagnosis] The diagnosis can be made according to the features of facial deformity. [Treatment] Facial deformities are usually treated by plastic surgery after adulthood, but auricular deformities affecting hearing should be treated by early auricular augmentation. [Prognosis] The prognosis is good and does not affect life. Only hearing impairment may cause mental retardation.