Mandibular hypoplasia

Mandibular hypoplasia

Description, Causes and Risk Factors:

Mandibular hypoplasia is a frequently encountered craniofacial difference and can be classified into three groups: congenital, developmental, and acquired. The focus of this article is on the congenital group, the majority of which is associated with syndromes. There have been numerous publications on patients with syndromic congenital mandibular hypoplasia; however, there has been no investigation and differentiation of the "non-syndromic" patients.

Broken down into its literal definition, mandibular hypoplasia means a jaw that is incomplete. "Mandibular" is the anatomical term referring to the lower jaw or jawbone and "hypoplasia" is a medical term that refers to an under development or growth of a part of the body. Mandibular hypoplasia therefore is the incomplete or under-development of the lower jaw. Micrognathism, a condition where the lower jaw is undersized, is another term meaning essentially the same thing.

Mandibular hypoplasia is often a congenital condition, but can also come about as a result of trauma or injury. The cause of congenital mandibular hypoplasia can vary and a cause is not always identified in pediatric patients born with this facial malformation. Similarly, mandibular hypoplasia may be only one of several specific underdevelopments that are the result of a birth defect. Other areas that may be affected include the ears, upper jaw, and nose.

Clinically, this condition may present as a deviated chin with asymmetrical facial features surrounding the mouth. Complications can occur and will depend largely on the severity of the condition, but can include difficulty breathing, chewing and swallowing, which can lead to sleep apnea and weight loss or failure to thrive in infants. In some cases, a tracheotomy or feeding tube may be necessary until surgical correction can be achieved.

Mandibular hypoplasia is classified as grade 2, 2, or 3. Grade 1 refers to mandibles that are small in size regardless of normal configuration. Grade 2 refers to mandibles that are hypoplastic, or underdeveloped, and may fall into subclasses A or B depending on the malformation. Grade 3 refers to a mandible that is severely underdeveloped or malformed.

A lot of cases of mandible hypoplasia have been reported in the literature, but the treatment of mandible hypoplasia generally was not mentioned in the literature because only early period treatment methods have been mentioned. Recurrence of fusion between the alveolar arches after separation of the maxilla and mandible have been reported. In the literature, a silicon block was used to keep the maxillary and mandibular alveolar arches separated.


The appearance of people with the disorder is caused by a loss of bone in the mandible which the body replaces with excessive amounts of fibrous tissue. In most cases, the condition fades as the child grows, but in a few even rarer cases the condition continues to deform the affected person's face. Mandibular hypoplasia also causes premature loss of the primary teeth and eruption of the permanent teeth.


Since this disease is genetically linked genetic counseling may be the only way to decrease occurrences of mandibular hypoplasia. The lack of severity of symptoms of the parents may be cause for failure to recognize the disorder. The optimal time to be tested for mutations is prior to having children. The disease results from a genetic mutation and this gene has been found to spontaneously mutate. Therefore there may be no prevention techniques available.


Treatment for mandibular hypoplasia requires reconstructive surgery. The extent of the surgery is dependent on the degree of underdevelopment and configuration of the surrounding facial bones and muscles. In essence, the mandible is rebuilt with a series of bone grafts. Reconstructive surgery is typically performed by an oral or maxillofacial surgeon, who will evaluate the condition and make recommendations based on medical history, development, severity of the condition, and age. This type of reconstructive surgery is quite complex, as the lower jaw serves many purposes and functions besides being a primary facial feature of an aesthetic nature. Nonetheless, many surgeries are quite successful at both improving facial features and correcting or alleviating complications that can occur because of hypoplasia.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


  1. Teresa Ward, RN

    Does this condition cause the jaw to be high risk for injury – is it easily fractured?

    • marko r

      There is no specific risk for injury in patients with manibular hypoplasia. The main additional problems are difficulty of breathing and risk of asphyxiation.

  2. Israel olabanji

    This is a great information. You have stated some point. I think this condition is not a life threatening?

    • maisteri

      Thank you for your comment! Yes, the condition itself typically is not life-threatening unless it’s associated with other diseases which affect various organ systems of the body and may have a poor outcome.


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