Micrognathism (or Micrognathia) is a condition where the jaw is undersized. It is also sometimes called "Mandibular hypoplasia". It is common in infants, but is usually self-corrected during growth, due to the jaws increasing in size. It may be a cause of abnormal tooth alignment and in severe cases can hamper feeding (Hong). It can also, both in adults and children, make intubation difficult, either during anesthesia or in emergency situations.
Hong P, Brake MK, Cavanagh JP, Bezuhly M, Magit AE. Feeding and mandibular distraction osteogenesis in children with Pierre Robin sequence: A case series of functional outcomes. Int J Pediatr Otorhinolaryngol 2012;76:414-418.