Syngnathia

Description

Syngnathia refers to congenital fusion of the maxilla and mandible. The fusion can be classified depending on the nature of the connecting tissue as either fibrous or bony fusion. Laster et al. (2001) proposed a classification for bony syngnathia into 4 types. Type 1a is simple anterior syngnathia characterized by bony fusion of the alveolar ridge only; type 1b is complex anterior syngnathia characterized by bony fusion of the alveolar ridges and also associated with other congenital malformations in the head and neck region; type 2a is simple mandibulozygomatic syngnathia characterized by bony fusion of the mandible to zygoma; and type 2b is complex mandibulozygomatic syngnathia characterized by bony fusion of the mandible to the zygoma and associated with cleft palate and/or temporomandibular joint ankylosis.

Clinical Features

Fuhrmann et al. (1972) described a new syndrome of cleft palate combined with multiple cordlike adhesions between the free borders of the palate and lateral parts of the tongue and floor of the mouth. The full syndrome occurred in 5 persons, a sixth had cleft palate only, and an unaffected male transmitted the disorder to 2 children with different mothers. The disorder was distinct from the ankyloglosson superius syndrome (106280).

Arshad and Goh (1994) reported 2 unrelated cases of hypoglossia congenita with anterior maxillomandibular fusion. One patient had hypoglossia with anterior maxillomandibular fusion, and the other had hypoglossia/hypodactylia with anterior maxillomandibular fusion.

Ugurlu et al. (1999) reported a newborn infant with no mouth opening bilaterally in the posterior region due to maxillary and mandibular bone fusion. In the front there was only was only 1 mm of mouth opening, and examination of the intraoral space could not be achieved. There were no other congenital anomalies. After surgery, an intraoral device which separated maxillary and mandibular alveolar arches from each other was designed and used for 8 weeks to avoid recurrence of the fusion. An adequate mouth opening was obtained, and the infant could be fed orally.

Villanueva-Garcia et al. (2009) reported a female infant, born to consanguineous parents, who was noted to have abnormal mobility of the mouth upon birth. She had prominent, everted vermilions, normal buccolabial sulci, and fused upper and lower gums with a small oral aperture. She had a prominent nose, marked micrognathia, and low-set, posteriorly rotated ears. She died at age 3 months due to airway obstruction. Imaging showed extensive fusion of the mandible with the maxilla and zygoma, and postmortem examination showed underdeveloped nares, palate, maxilla, and mandible. The oral cavity was very small and contained a rudimentary tongue. The mandibular rami were completely fused to the maxillary tuberosities and zygoma, with ankylosis of the temporomandibular joint. No other abnormalities were detected.

Halli et al. (2010) reported an 8-year-old boy who had a congenital facial deformity and was unable to open his mouth since birth. He had an everted lower lip and facial asymmetry due to unilateral maxillomandibulozygomatic fusion on the left side. This was associated with temporomandibular joint ankylosis, consistent with type 2B in the classification of Laster et al. (2001). The patient had no other congenital anomalies. Surgery and physiotherapy resulted in improvement.

Inheritance

Gassner et al. (1979) reported the disorder in mother and child. They suspected that this is the same disorder as that reported by Fuhrmann et al. (1972). Gorlin (1982) saw the syndrome in a father and son.

Affected families reported by Fuhrmann et al. (1972), Gassner et al. (1979), and Gorlin (1982) suggested autosomal dominant inheritance, whereas the patient reported by Villanueva-Garcia et al. (2009) was born of consanguineous parents, suggesting autosomal recessive inheritance.