Micrognathia

Micrognathia is a congenital condition defined by an undersized mandible (lower jaw), which can give the appearance of a receding chin. It may occur as an isolated anomaly or as part of a broader craniofacial syndrome. The clinical impact ranges from minimal to significant, with more pronounced cases potentially causing feeding difficulties and airway obstruction, especially in newborns.

Causes and associations: Micrognathia results from impaired development of the mandible during embryogenesis, most often involving disturbances of the first pharyngeal arch. It frequently appears as part of genetic or syndromic conditions, such as Pierre Robin sequence (micrognathia with glossoptosis and sometimes cleft palate), Treacher Collins syndrome, Nager acrofacial dysostosis, and other craniofacial disorders. Isolated micrognathia can also occur and may be familial or sporadic. It is important to assess for associated anomalies and syndromes when micrognathia is identified.

Clinical features and complications: The hallmark is a smaller-than-normal mandible, which can create retrognathia and airway crowding. In infancy, this may contribute to feeding challenges, sleep-disordered breathing, or obstructive symptoms. The condition may be more noticeable when the tongue shifts posteriorly (glossoptosis) or when there is associated cleft palate.

Diagnosis and evaluation: Diagnosis is typically clinical, supported by imaging. Lateral skull radiographs or CT/MRI studies help define the extent of mandibular hypoplasia and evaluate the airway. Prenatal imaging with ultrasound or fetal MRI can sometimes detect facial profile abnormalities suggestive of micrognathia before birth. Genetic testing and multidisciplinary assessment are common when a syndrome is suspected.

Management and prognosis: Mild isolated cases may require only observation, with attention to growth and dental alignment. More significant cases may need airway and feeding support. Treatments range from positioning and noninvasive airway strategies to surgical options such as mandibular distraction osteogenesis or advancement, tongue-lip adhesion, and, rarely, tracheostomy. Prognosis varies with severity and underlying etiology; many patients improve as growth progresses, particularly in non-syndromic forms.